To provide a beating assembling structure for a legless chair improved so as to attain improvement in assembly ability.

This structure is provided with a back frame 31 for supporting a back cushion and a side frame 42 for supporting the back frame 31, and a reclining shaft 6 integrally provided with a flange 62 is interposed between the back frame 31 and the side frame 42 and a bolt inserting hole 621 is bored on the flange 62. On the other hand, a bracket 311 is provided with a bolt inserting hole 313 corresponding to the bolt inserting hole 621 and a nut N, an axial hole 42a for supporting the fram 42 by letting the reclining shaft 6 pass through is bored on the side frame 42, and a bolt bead passing hole 44, through which the head of a bolt can be passed, is bored at a position opposite to the bolt inserting hole 621.