A calibration method in which, a rotation angle calculation device (20, 30) calculates (S2) a rotation angle θc based on a detection signal of a sensor, transmits (S3) rotation angle data Dc indicating the rotation angle θc to a calibration device (40), and transmits (S3) time difference data Dt relating to a time difference after having captured the detection signal until transmitting the rotation angle data to the calibration device, and in which the calibration device measures (S1) a rotation angle θr, clocks (S1, S4) a measurement time tm at which the rotation angle θr is measured and a transmission time tt of transmitting or receiving the rotation angle data, and acquires (S5, S6) calibration data Dc of the rotation angle data by comparing the rotation angle θr measured at a time tc2 obtained by going back in time from the transmission time tt by the time difference after having captured the detection signal until transmitting the rotation angle data and the rotation angle data Da with each other.