A wind turbine group power generation amount evaluation device for evaluating a power generation amount of a wind turbine group including a plurality of wind turbines, comprising: a wind direction acquisition unit configured to acquire a wind direction acting on the wind turbine group; a criterial correlation acquisition unit configured to acquire a criterial correlation which is a correlation between a target power generation amount (Pt) by a target wind turbine group (Gt) and a reference power generation amount (Pr) by a reference wind turbine group (Gr), the target wind turbine group (Gt) being the wind turbine group of an evaluation target having, as members, n wind turbines disposed along the acquired wind direction, n being an integer greater than or equal to 2, the reference wind turbine group (Gr) having, as members, the wind turbines which are not the members of the target wind turbine group (Gt) and are disposed along the wind direction, the reference wind turbine group (Gr) being disposed in parallel to the target wind turbine group (Gt); a set value changing unit configured to change a set value of an output control parameter of at least one of the wind turbines in the target wind turbine group (Gt); a power generation amount acquisition unit configured to acquire the target power generation amount (Pt) and the reference power generation amount (Pr) measured after the change in the set value; a target power generation amount estimation unit configured to calculate, based on the criterial correlation and the reference power generation amount (Pr') acquired after the change, an estimated value before the change of the target power generation amount (Pt) which corresponds to the reference power generation amount (Pr') acquired after the change; and an evaluation unit configured to evaluate a target power generation amount (Pt') after the change based on a comparison between the target power generation amount (Pt') after the change and the estimated value before the change. a wind direction acquisition unit configured to acquire a wind direction acting on the wind turbine group; a criterial correlation acquisition unit configured to acquire a criterial correlation which is a correlation between a target power generation amount (Pt) by a target wind turbine group (Gt) and a reference power generation amount (Pr) by a reference wind turbine group (Gr), the target wind turbine group (Gt) being the wind turbine group of an evaluation target having, as members, n wind turbines disposed along the acquired wind direction, n being an integer greater than or equal to 2, the reference wind turbine group (Gr) having, as members, the wind turbines which are not the members of the target wind turbine group (Gt) and are disposed along the wind direction, the reference wind turbine group (Gr) being disposed in parallel to the target wind turbine group (Gt); a set value changing unit configured to change a set value of an output control parameter of at least one of the wind turbines in the target wind turbine group (Gt); a power generation amount acquisition unit configured to acquire the target power generation amount (Pt) and the reference power generation amount (Pr) measured after the change in the set value; a target power generation amount estimation unit configured to calculate, based on the criterial correlation and the reference power generation amount (Pr') acquired after the change, an estimated value before the change of the target power generation amount (Pt) which corresponds to the reference power generation amount (Pr') acquired after the change; and an evaluation unit configured to evaluate a target power generation amount (Pt') after the change based on a comparison between the target power generation amount (Pt') after the change and the estimated value before the change.