PURPOSE: To make small an operation clock cycle of an entire circuit device by a method wherein clock skew at an external terminal for clock observation of each printed wiring board is reduced to the minimum, in the circuit device constructed of a number of printed wiring boards.

CONSTITUTION: In each wiring board 1, clock supply lines 4a to 4e from IC 3 for clock supply to ICs 2a to 2e and clock supply lines 5a to 5e from the ICs 2a to 2e to observation terminals 6a to 6e corresponding to the ICs respectively are made equal in length respectively. A relay terminal 7 for relaying a clock for observation to an external terminal 9 and one of the observation terminals 6a to 6e are connected with each other by a wiring 10. When one of the observation terminals which has a phase being nearest to the midpoint of the maximum of a clock phase shift at each observation terminal is selected and connected to the relay terminal, clock skew of each wiring board becomes minimum and a clock cycle of an entire circuit device can be made small.