To solve the problems that a head module becomes large in the case of a configuration in which a head drive signal generating means and a head control signal generating means are mounted in the head module with a plurality of heads arranged therein, and that the number of harnesses increases if the means are mounted to the side of an apparatus body control part.

The head drive signal generating means 513 which generates a head drive signal for driving each head 1010 of the head module 51 is set at the side of an apparatus body. A position information storing means 521 which stores position information to a reference position of the head module 51, and the head control signal generating means 522 which generates a head control signal necessary for driving the control of the head 101 other than the head drive signal are set in a relay substrate 108 of the head module 51.