To provide a connection device for pipe materials which can be more easily handled and makes it possible to construct a safe and stable temporary structure and by which construction and demolition can be carried out simultaneously.

This connection device is constituted of a spacer 2 firmly fixed to an appropriate position of a chief column pipe 1 while radially protruding a plurality of engaging projections 20 having fitting female parts 21 at the nearly central part, and a top plate 30 protruding a fitting male part 33 having a shape to fit to the fitting female part to the inside face of the front end, side walls 31 hanging down from the both sides of the top plate and wrapping the engaging projection, a basal part 32 attaching a member 4 to be connected for connection to the chief column pipe 1 at the rear end of the top plate, a cylindrical slide body 34 wrapping the top plate, the side walls, and the engaging projection and having a width in which the front end does not interfere with the engaging projection during retreating at the basal end, a locking body 35 for the slide body protruded at the foremost part of the top plate, an insertion hole 36 formed on the top plate which positions at the front side of the slide body when the slide body retreats extremely and positions at the rear side of the slide body when it advances extremely, and a locking pin 5 which can be inserted in the insertion hole to prevent advance or retreat of the slide body.