A court in Casablanca Thursday handed out prison sentences ranging from one month to one year to 14 heavy metal music enthusiasts, the official MAP news agency reported.
The trial followed articles in some newspapers which described the accused as "Satanists" who recruited for an international cult of devil-worship.
The 14 men, aged between 22 and 35 years, were found guilty of "possessing objects which infringe morals" and of "acts capable of undermining the faith of a Muslim."
Morocco's penal code allows a maximum sentence of three years for attempting to convert a Muslim to another faith.
Nine of those sentenced are musicians in three Moroccan heavy metal groups: Nekros, Infected Brain and Reborn.
Parents, friends and college supervisors of those sentenced had argued that the case arose from a misunderstanding of the heavy metal subculture and should never have come to court.
Soumayah Kortbi, whose 31-year-old brother Ayoub Kortbi was sentenced to three months, said, "I am disappointed with justice in my country. It is as though the court did not take the trouble to find out the facts."