A calibration device for a work machine includes: a measurement value acquiring unit acquiring respective measurement values of a first actuation unit and a bucket measured using an external measurement device; a working equipment parameter acquiring unit acquiring working equipment parameters of the member of the first actuation unit and the bucket; a calibration unit calibrating the working equipment parameters of the member of the first actuation unit and the bucket based on the measurement value of a reference point of the bucket acquired by the measurement value acquiring unit; and a calibration range selecting unit selecting, from among a first range where a variation in a swing angle of the bucket has a predetermined relationship with a change in swing angle information of the bucket and a second range where a variation in the swing angle increases as compared with the variation in the first range.