Uniforming of the processing load is efficiently realized. Each processing element configuring an SIMD parallel computer system includes a data storage module that stores data processed or transferred, a number-of-data-sets storage device that stores number of data sets, and a front data storage device that stores the front data. Each processing element further includes a control processor that compares the number of data sets stored in one processing element with the number of data sets stored in the own processing element, and issues a data distribution leveling instruction that designates an action for updating contents of the data storage module, the number-of-data-sets storage device, and the front data storage device according to a rule determined based on a comparison result of the own processing element and that of the other processing elements and an action for moving the data stored in the one processing element to the own processing element.