To provide a junction structure having a relatively simple structure in a steel construction which is not suddenly broken even when a breaking load such as an earthquake acts on the steel construction.

Reinforcements 25 as reinforcing members in a joint 20 for a steel structure are arranged so as to stick to the inside space of an upper column 12 and a lower column 10 made of steel pipes. And concrete 29 is placed in the inside space of the upper column 12 and the lower column 10 and the inside space of a butt end core 21 to integrally form the upper column 12, the lower column 10, and the joint 20. In this way, the vertical direction is connected by a reinforced concrete column with reinforcing members. And hence, a simple connection structure without fear that it is suddenly broken by horizontal vibration in particular like a welding structure, can be obtained.