The drive device (12) includes an output voltage decomposition unit (1221) that decomposes an output voltage to the ultrasonic transducer into a basic component and a harmonic component, and an output current flowing through the ultrasonic transducer to a basic component and a harmonic component. An output current decomposition unit (1222) that decomposes into a Cb current, a Cb current calculation unit (1223) that calculates a basic component and a harmonic component of the Cb current based on a basic component and a harmonic component of the output voltage, and an output current A drive current calculation unit (1224) for calculating the fundamental component and the harmonic component of the drive current of the ultrasonic transducer based on the fundamental component and the harmonic component of the Cb current, and the fundamental component and the harmonic component of the Cb current； A drive current summing unit (1226) that sums up the current component and the harmonic component, and a constant current control unit (1227) that generates constant current control data so that the summed drive current becomes a target value.駆動装置(12)は、超音波振動子への出力電圧を基本成分と高調波成分とに分解する出力電圧分解部(1221)と、超音波振動子に流れる出力電流を基本成分と高調波成分とに分解する出力電流分解部(1222)と、出力電圧の基本成分及び高調波成分に基づいて、Ｃｂ電流の基本成分と高調波成分とを算出するＣｂ電流算出部(1223)と、出力電流の基本成分及び高調波成分と、Ｃｂ電流の基本成分と高調波成分とに基づいて、超音波振動子の駆動電流の基本成分及び高調波成分を算出する駆動電流算出部(1224)と、駆動電流の基本成分及び高調波成分を合算する駆動電流合算部(1226)と、合算された駆動電流が目標値となるように定電流制御データを生成する定電流制御部(1227)とを備える。
