PURPOSE: To closely combine a large-scale-system composed of many components through many wirings by mutually combining pipe-shaped modules through arranging connection terminals in the outer walls of pipe-shaped circuit modules.

CONSTITUTION: Circuit devices 10 are mounted on the inner wall surfaces la of each circuit module 1 of pipe structure. Then, the connection between devices in a pipe is effected by wirings formed in the pipe itself and the connection with the circuit devices 10 of other adjacent modules l is effected via electric contacts 11 formed in the pipe outer wall surfaces 1b of each circuit module 1. In addition to the wirings in pipe, i.e., wirings from the circuit devices 10 of the pipe inner wall surfaces to the electric contacts 11 of the pipe outer wail surfaces 1b are formed in the circuit module 1. Also, a cooling fan module 5 can be attached to the lower end of the circuit module 1 so that cooling of the device is effected without hindrance even if the circuit devices are mounted with a high density.