A multifunction peripheral device capable of being operated in a plurality of switchable operational modes is provided. The multifunction peripheral device includes a reader unit with a light source and a light receiving element to receive the light reflected on the original document to generate image data, operation receiving members, through which a user's instructions are entered, a valid instruction storage unit to store valid instruction information, which defines correspondence between a valid instruction and a valid instruction receiving member, a judging unit to judge as to whether an operation entered through one of the operation receiving members is the valid instruction based on the valid instruction information and a current operational mode, and a switching unit to switch the light source on when the judging unit judges that the entered operation is the valid instruction.