Muñoz was originally from the town of Vélez-Málaga, Spain. The municipality is the capital of the Axarquía comarca in the province of Málaga, in the Spanish autonomous community of Andalusia.
Muñoz won her local city pageant, Miss Vélez-Málaga, in 1973 and the chance to compete for the title of Miss Spain. Muñoz won the pageant and the title of Miss Spain 1973. The win qualified her to represent her country at the 23rd annual Miss Universe Pageant.
Muñoz competed against 64 other contestants for the coveted title. She was crowned Miss Universe 1974 on July 21, 1974 at the Folk Arts Theater located in Manila, Philippines. It was the first time the Miss Universe Pageant was held in Asia.
Later that year, Muñoz was forced to resign her title. Muñoz refused to follow organizational rules and refused to go on a trip to Japan. The organization did not have another contestant take her place.
Afterwards, the film industry took a great interest in Muñoz. She appeared in numerous films including Mama Turns 100, Clara es el Precio, The Other Bedroom and Dedicatory.
While working on The Other Bedroom in 1976, Muñoz met singer-songwriter Patxi Andión. The two married in 1976 but divorced two years later.
In 1979, while working on Mamá cumple cien años which was nominated for the Academy Award for Best Foreign Language Film at the 52nd Academy Awards, Muñoz met Elías Querejeta. The two had a relationship but Querejeta remained married, although he and his wife had been living separate lives. There was never an official split and neither party pursued a divorce. Muñoz did not interfere and never fought for marriage.
Muñoz died of unspecified causes on February 27, 2011 at the age of 56.