The skydiver's main parachute spun out of control Thursday and his secondary chute wasn't deployed, The (Stockton) Record reported.
The skydiver at the Acampo Parachute Center was not identified, pending notification of his family.
Paramedics tried to revive the man.
"The only thing we know is he had an open main parachute spinning violently. Why he did not use his extra [chute] is beyond us," said Bill Dause, the owner of the parachute center.
San Joaquin County Sheriff's Office officials were conducting a coroner's investigation, Deputy Les Garcia said.
The investigation will be turned over to the Federal Aviation Administration, which handles skydiving deaths, Garcia said.