Disclosed is a printer which performs efficient power save control by keeping track of the condition of each client of the printer without having to send wasteful packets, that is, without affecting the network environment. The printer includes: a unit for monitoring packets flowing on a network, and for updating and storing a client-associated last receive time each time a packet is received from any client of the printer; a unit for determining, by referring to the stored client-associated last receive time, that any client from whose associated last receive time has elapsed a prescribed time is in an idle condition, and for computing a printer usage rate by summing the past average usage rates of the clients that have been determined not to be in an idle condition; and a unit for setting, based on the computed printer usage rate, the length of time allowed before a transition is made to the power save mode.