To provide an inter-planetary space communication network system that requires no large installation even in the case of communication for a long distance in an inter-planetary space.

A plurality of communication artificial planetary devices 10-13, 20-27, 30-41, 50-65 are placed on a plurality of circular orbits (radii, r, 2r, 3r, 4r) around the sun 3 respectively at an equal interval. Communication stations 1, 2 flying an inter-planetary space make communication with each other by using the communication artificial planetary devices 56, 35, 24, 25, 38 for relay stations. Thus, a small antenna is enough for the communication stations 1, 2 and the transmission power is reduced. Moreover, even when the sun 3 is in existence between the communication stations 1, 2, they can make communication with each other.