In a game played by a plurality of game machines through teamwork, an evaluation is performed according to the correlation among operation information obtained through communications with each of the game machines. A plurality of game machines communicate with one another to establish timing synchronization. After the game, input timings at which buttons are operated during the game are collected and then evaluated so as to determine an absolute and relative timing coincidence in a predetermined period (unison part). A predetermined number of points are added to its game score based on the evaluation.