PURPOSE: To elevate a temperature quickly while simultaneously removing bubbles when the temperature of a head is lower than an ambient temperature.

CONSTITUTION: Maintenance operation is conducted in a head at the time of start-up after the head is left for a prolonged time as it is. A CPU1 confirms positioning at a home position, and detects a temperature by a signal from a head-temperature detecting section 3, and the double frequency of normal printing frequency is selected in the frequency of a frequency generating section 15 when the temperature of the head is low. The head 13 is driven by the double frequency by a head controller 12, and empty discharge is conducted while the same signal as the driving signal of the head 13 is transmitted over a vibrating section 14, thus applying vibrations to the head.