To provide a means capable of suppressing the enlargement of a device and the increase of power consumption, and efficiently reducing electromagnetic noise in relatively simple constitution.

A printed board (e) (insulation board) provided with a grounding conductor (f) on the back surface, has on its surface a signal line (a) of a pattern wiring for transmitting high speed signals to be the generation source of noise, a signal line (d) which is pattern wiring for transmitting relatively low speed signals near the signal line (a), and a signal line (b) arranged as pattern wiring roughly in parallel along the signal line (a) between the signal line (a) and the signal line (d). By transmitting the signals through the signal line (a) in an opposite direction to the signal line (b), the signal line (b) is made to generate an electromagnetic field for offsetting an electromagnetic field generated from the signal line (a), and the electromagnetic noise is reduced as radiated to the space from the signal line (a) of the generation source of the noise.