A calculation apparatus 100 includes an encoder 101 configured to detect rising edges of PWM signals having at least three or more phases in each of the phases, and a register 103 configured to store, at a timing after the PWM signals having the respective phases rise and after AD conversion of a current value of a drive signal of a motor obtained by the PWM signals, a difference value between the AD-converted current value and a previous AD-converted current value for each phase.