A power generation control device of a vehicle alternating current generator, for controlling generator output to a predetermined range by intermittently controlling a field current of the vehicle alternating current generator, the power generation control device comprising: a limit deactivation signal reception unit configured to receive a limit deactivation signal of the field current from an exterior; a rotation speed detection unit configured to detect generator rotation speed; a temperature detection unit configured to detect temperature of the power generation control device; and a limit activation/deactivation determination unit configured to, when the limit deactivation signal is input, deactivate a field current limit, and thereby increase the generator output, by allowing the limit deactivation signal when the generator rotation speed is equal to or greater than a predetermined value and the temperature of the power generation control device is lower than a predetermined value, and keep the field current limit activated by disallowing the limit deactivation signal when the generator rotation speed is lower than the predetermined value or the temperature of the control device is equal to or higher than the predetermined value, further comprising: a field duty detection unit for detecting a field duty which is an electricity supply continuity rate to the field coil of the generator; a limit duty generation unit for generating a predetermined limit duty in accordance with signals from the limit activation/deactivation determination unit; and a timer unit for measuring a deactivation time from the field duty reaching the limit duty, wherein when the limit deactivation signal of the field current is received from the exterior and deactivation is allowed, the deactivation time is measured, the field current limit is reactivated when a cumulative value of the deactivation time reaches a predetermined timer time, and the cumulative time is reduced after the cumulative time reaches the timer time, and deactivation of the field current limit is enabled again when the cumulative value decreases to a recovery time after once reaching the timer time and the field current limit being activated. a limit deactivation signal reception unit configured to receive a limit deactivation signal of the field current from an exterior; a rotation speed detection unit configured to detect generator rotation speed; a temperature detection unit configured to detect temperature of the power generation control device; and a limit activation/deactivation determination unit configured to, when the limit deactivation signal is input, deactivate a field current limit, and thereby increase the generator output, by allowing the limit deactivation signal when the generator rotation speed is equal to or greater than a predetermined value and the temperature of the power generation control device is lower than a predetermined value, and keep the field current limit activated by disallowing the limit deactivation signal when the generator rotation speed is lower than the predetermined value or the temperature of the control device is equal to or higher than the predetermined value, further comprising: a field duty detection unit for detecting a field duty which is an electricity supply continuity rate to the field coil of the generator; a limit duty generation unit for generating a predetermined limit duty in accordance with signals from the limit activation/deactivation determination unit; and a timer unit for measuring a deactivation time from the field duty reaching the limit duty, wherein when the limit deactivation signal of the field current is received from the exterior and deactivation is allowed, the deactivation time is measured, the field current limit is reactivated when a cumulative value of the deactivation time reaches a predetermined timer time, and the cumulative time is reduced after the cumulative time reaches the timer time, and deactivation of the field current limit is enabled again when the cumulative value decreases to a recovery time after once reaching the timer time and the field current limit being activated. a field duty detection unit for detecting a field duty which is an electricity supply continuity rate to the field coil of the generator; a limit duty generation unit for generating a predetermined limit duty in accordance with signals from the limit activation/deactivation determination unit; and a timer unit for measuring a deactivation time from the field duty reaching the limit duty, wherein when the limit deactivation signal of the field current is received from the exterior and deactivation is allowed, the deactivation time is measured, the field current limit is reactivated when a cumulative value of the deactivation time reaches a predetermined timer time, and the cumulative time is reduced after the cumulative time reaches the timer time, and deactivation of the field current limit is enabled again when the cumulative value decreases to a recovery time after once reaching the timer time and the field current limit being activated.