A system controller includes an output unit which transfers an access request from an access source coupled to the system controller to an other system controller; a local snoop control unit that determines whether a destination of the access request from the access source is a local memory unit coupled to the system controller, and locks the destination when the destination is the local memory unit; a receiving unit which receives the access request from the output unit and an access request from an other system controller; a global snoop control unit which sends a response indicating whether the access request is executable or not, and controls locking of the destination of the access request when the destination is the local memory unit; and an access processing unit which unlocks the locking and accesses the memory unit when the access request from the access source becomes executable.