This invention relates to a connecting mechanism for structural members, used so as to connect together structural members, which are to be assembled into a structure, and establish communication between the passages defined by these structural members. A conduit communicating member (42) is inserted into a first passage (30) in one structural member (20), and the head portion of this member (42) is fitted in a groove (22) in another structural member (20a). The passage (30) in one structural member and that (30) in the other communicate with each other via a through bore provided in the conduit communicating member (42). A first locking member (44) is inserted into a recess (29a) in one structural member, and a second locking member (46) is held in the groove (22) in the other structural member. The first and second locking members (44, 46) are combined with each other via a locking member (48), whereby these two structural members are connected and fixed firmly.