To provide a construction method of a reinforced concrete column/steel beam building facilitating construction and shortening a construction period by performing concrete placing of a column part and an upper floor at the same time.

In this construction method, a form composed of a plurality of form members 13 in a circumferential direction surrounding the periphery of a column forming space 11 is used as a column form 10. The column form 10 has beam placing recessed parts 15 at the upper end to place steel beams 2 in a fitted state, and has strength that can support load when constructing steel beams and upper floor slabs. In this construction method, arrangement of reinforcements 1 of a lower floor column and construction of the column form 10 are performed first. In the following process, the steel beams 2 of the upper floor are placed in the beam placing recessed parts 15 of the constructed column form 10, and a blocking material 4 for blocking the periphery of a concrete placing space used as a joint part between the steel beam 2 and column is disposed. A deck plate of the upper floor is then laid, and placing of column concrete 8 in the column form 10, placing of concrete onto the joint part, and placing of slab concrete 9 of the upper floor are performed.