A PCM (50) that is an engine control device functions to acquire a master vac negative pressure which is the negative pressure of a stabilized chamber of a master vac (126) which amplifies a brake pedal depressing force applied to a brake pedal (102), and also acquire a brake working fluid pressure that is a braking hydraulic pressure produced by a master cylinder (144) in accordance with the brake pedal depressing force amplified by the master vac (126), and in a case where both accelerator pedal (104) and a brake pedal (102) are depressed or actuated simultaneously, determine whether or not it is necessary to decrease engine output based on such master vac negative pressure and brake working fluid pressure to execute the output decreasing control for decreasing the engine output.