A stepper motor control device, comprising: a sensor that detects physical quantities; and a control device that operates a stepper motor based on data corresponding to the physical quantities sent from the sensor, wherein the control device implements a target rotational angle computation process that calculates a target rotational angle of a drive shaft of the stepper motor based on data corresponding to the physical quantities sent from the sensor; a target rotational angle change computation process that calculates a target rotational angle change which is a difference between a present rotational angle (Dx-1) of the drive shaft of the stepper motor and the target rotational angle; a divisional target rotational angle (RΘ) computation process that divides the target rotational angle change by a first divisional target rotational angle (RΘ) within a range not exceeding the rotational limit for loss of synchronism of the stepper motor to calculate a "quotient" and a "remainder" thereof; and the control device is a drive control device of the stepper motor that sets the "quotient" to "quotient + 1" in the case the "remainder" portion is not 0 and obtains a second divisional target rotational angle (RΘ) differing from the first divisional target rotational angle (RΘ) which is a value calculated by the divisional target rotational angle (RΘ) computation process as a rotational angle per one control period, and drives the stepper motor by supplying to the stepper motor the second divisional target rotational angle (RΘ). a sensor that detects physical quantities; and a control device that operates a stepper motor based on data corresponding to the physical quantities sent from the sensor, wherein the control device implements a target rotational angle computation process that calculates a target rotational angle of a drive shaft of the stepper motor based on data corresponding to the physical quantities sent from the sensor; a target rotational angle change computation process that calculates a target rotational angle change which is a difference between a present rotational angle (Dx-1) of the drive shaft of the stepper motor and the target rotational angle; a divisional target rotational angle (RΘ) computation process that divides the target rotational angle change by a first divisional target rotational angle (RΘ) within a range not exceeding the rotational limit for loss of synchronism of the stepper motor to calculate a "quotient" and a "remainder" thereof; and the control device is a drive control device of the stepper motor that sets the "quotient" to "quotient + 1" in the case the "remainder" portion is not 0 and obtains a second divisional target rotational angle (RΘ) differing from the first divisional target rotational angle (RΘ) which is a value calculated by the divisional target rotational angle (RΘ) computation process as a rotational angle per one control period, and drives the stepper motor by supplying to the stepper motor the second divisional target rotational angle (RΘ). sets the "quotient" to "quotient + 1" in the case the "remainder" portion is not 0 and obtains a second divisional target rotational angle (RΘ) differing from the first divisional target rotational angle (RΘ) which is a value calculated by the divisional target rotational angle (RΘ) computation process as a rotational angle per one control period, and drives the stepper motor by supplying to the stepper motor the second divisional target rotational angle (RΘ).