A gap-coupling bus system in which data can be transferred between all modules connected to a bus. The gap-coupling bus system has at least three modules (11-16) which each have at least one transmission/reception circuit, at least three signal lines (21-16) whose one ends are connected to the modules (11-16) respectively, and terminating resistors (31-36) which are connected to the other ends of the signal lines (21-26) and whose resistance values are nearly the same as the characteristic impedances of the signal lines (21-26). The at least three signal lines (21-26) have portions (1-2, 1-3, 2-3, ...) where the signal lines of two different modules among the at least three modules (11-16) are in parallel with each other.