To calculate a characteristic value of a pump with high accuracy without measuring operation characteristic data of the pump in advance.

A device for calculating a pump characteristic value includes: a reference operating point identifying part 16A for dividing a flow rate in control Q₁ of an input characteristic value by a rotational speed ratio in control INV₁, thereby calculating a reference flow rate Q₀ at a reference operating point R₀ at reference rotational speed N₀; and a reference point-of-power identifying part 16B for identifying a reference point of power P₀ at the reference rotational speed N₀ based on the reference flow rate Q₀ at the reference operating point R₀ and a reference shaft power curve B₀, thereby calculating reference shaft power E₀ at a reference point of power P₀. In a characteristic value calculating part 16C, a shaft power curve in control B₁ is identified based on the reference flow rate Q₀ and the reference shaft power E₀ at the reference point of power P₀. Shaft power in control E₁ at rotational speed in control N₁ is calculated as an output characteristic value from the shaft power curve in control B₁ and the flow rate in control Q₁.