To properly control revolution speed in order to obtain a maximum electric power.

This variable speed wind power generation system comprises: setting equipment 15, 16 for setting a windmill parameter corresponding to a wind velocity; a computing unit 22 for computing a generated energy of an induction generator 1; and a revolution speed control instruction calculator 8 for calculating a revolution speed control instruction based on the windmill parameter, the generated energy, and the revolution speed of the induction generator 1. The windmill parameter is constituted only of three functions of an output set value P(V), a revolution speed set value N(V), and a pitch angle set value θ(V) which are described by the wind velocity (V). By defining values of the three control variables corresponding to the wind velocity, proper and efficient control of an output of the induction generator or the revolution speed corresponding to the output is performed. Based on a magnitude relation of the output set value P(V) and the revolution speed set value N(V) corresponding to a rated output PRAT and rated revolution speed NG of the induced generator 1, limiters 34, 38 are added which regulate a pitch angle instruction θSET with respect to the windmill 2 and an output instruction PSET with respect to the induced generator 1 so that the instructions are within respective set regions. An excessive increase of revolution speed is effectively and simply prevented by such a control logic.