Homeless Deyan Deyanov, 29, was convicted by a jury of nine at the Provincial Court in Santa Cruz de Tenerife.
He repeatedly stabbed and beheaded Jennifer Mills-Westley, 60, who had been shopping in the popular resort of Los Cristianos on 13th May, 2011.
Deyanov had denied murder. His defence had argued he was not criminally responsible for his actions because he suffers acute paranoid schizophrenia.
He faces a sentence of 15 to 20 years in a psychiatric unit.