A grid computing system includes a plurality of nodes for processing a plurality of jobs, and a management apparatus for managing the plurality of the nodes. Each of the nodes is switchable between a standby and an active status, respectively. And the management apparatus including, a job request unit for allotting a plurality of requests of jobs to any of the nodes in an active state, a prediction unit for predicting the number of the nodes in the active state optimal for predicted amount of jobs requested from the exterior at a future time when a predetermined time period lapses from the present time, and a controller for controlling switching of the nodes between the standby and active so as to control the predicted number of the nodes to start switching before the future time.