Alberto Martin-Artajo, who as Spanish foreign minister between 1945 and 1957 broke through the diplomatic isolation of post-war Franco Spain, died here yesterday at the age of 74.

Mr. Martin-Artajo died in a hospital from an acute stomach infection. His family said he had been ill for some time.

As foreign minister he lived through the most difficult moments of General Franco's regime. Following the Allied World War II victory, the United Nations boycotted the Spanish dictatorship and all but three foreign legations withdrew their ambassadors from Madrid.

By the end of his 12-year term of office, Mr. Martin-Artajo had broken through the diplomatic siege securing recognition from the Vatican and the United States.

In 1953 the Vatican, under the papacy of Pius XII, signed a concordat with the Spanish government that ensured General Franco's sole recognition of Catholicism among organized religions and Catholic teaching in schools in return for a government veto on the Vatican's appointment of bishops. The same year the Franco regime earned the recognition of the United States in return for a bases agreement that, following subsequent renewals and amendments, is still in force.

Mr. Martin-Artajo was aided in his achievements by his strong Catholic background and by the onset of the cold war. A member of Catholic Action during the Spanish Republic of the 1930s, he joined General Franco's uprising against the government and acted as a legal adviser to the Falange. After the war he set up a lawyer's practice in Madrid and became president of the Catholic Action pressure group.

His appointment to the foreign minister's post came with a brief to restore relations with the rest of the world after the United Nations ostracism. As East-West relations deteriorated he was able to secure friendship with the U.S. due to the strong anti-communism of the Franco regime and the strategic importance of the Iberian Peninsula.

Mr. Martin-Artajo was succeeded in the foreign ministry by his protege, Fernando Maria Castiella, who implemented the guidelines he had laid down for what was to be Franco's foreign policy for the next 20 years: close ties with the Arab world and with Latin America and a dependence on Washington boosted by the blessings of Rome. Although Western European governments finally recognised the Franco government, the nature of the regime barred Spain from the European Community and the Atlantic Alliance.

After leaving office, Mr. Martin-Artajo devoted his energies to the Spanish Catholic Press Publishing Group of which he was chairman. The group runs several newspapers, a news agency and a publishing company. He also acted as a constitutional adviser to the government.

A widower, Mr. Martin-Artajo leaves seven sons and one daughter.