A head substrate for mounting a driver IC that selectively drives a plurality of driving elements is provided. An input signal wiring pattern electrically connects external connection terminals with the pads in a first pad array and a second pad array. The input signal wiring pattern includes a clock signal line for supplying the clock signal to the driver IC and a logic power line for supplying the logic power to the driver IC. A part of the clock signal line and a part of the logic power line are disposed between the first pad array and the second pad array.