The attorney general's office says the remains of 129 bodies have been recovered from the graves.
None of the remains have been linked to the students who vanished in Iguala.
The information was released after a freedom of information request by the Associated Press.
The majority of the bodies are male, but the remains of some 20 women were also found.
The unmarked graves were discovered during the huge investigation into the disappearance of the 43 students.
The number of mass graves found from October to May could be higher because the information given to AP only covers instances in which specialists became involved.
The students, from a teachers' college in Guerrero, had travelled to Iguala and, as part of a protest, commandeered a number of buses.
The government says the 43 were intercepted by police and handed to members of a drugs gang who killed them and incinerated their bodies.
Gang members confessed to killing the students and burning their bodies after they were mistakenly told they belonged to a rival gang.
The badly burnt remains of one student have been found at a rubbish dump, but many families of the remaining 42 refuse to believe the students are dead.
Correspondents say the case has highlighted the huge number of people who have gone missing in Mexican states where drug violence is widespread.
Sixty mass graves have been uncovered in the southern Mexican state of Guerrero during a search for 43 student teachers abducted last September, official documents have revealed.