A parallel computer system comprising a node group having numbers of nodes connected by a network, in which a job scheduler of a job server that schedules jobs to be executed by a node of the node group comprises a temperature calculating unit which with a node being used of the node group as an imaginary heat source and with the assumption that a quantity of heat is conducted from the heat source to a surrounding node, calculates a temperature of a surrounding free node based on a distance from the heat source, a free region extracting unit which selects, from a plurality of temperature groups obtained by grouping free nodes on a certain temperature range basis, a temperature group meeting the number of free nodes required by a job according to a temperature and takes out a lowest temperature free node from the selected temperature group as a center node, and a node selecting unit which sequentially selects the necessary number of free nodes starting with a shortest distance free node centered around the center node.