To provide a gutter structure of a building capable of efficiently draining even in a long inner balcony and mounting it with a few site works.

The inner balcony 16 of the building is divided into a plurality of sections 16A to 16C in the longitudinal direction, columns 51 and 52 are erected among the 16A to 16C to form the gutter structure of the building, the drainage of the inner balcony 16 flows toward one column 51 from the first and second balconies 16A and 16B adjacent to each other, and it flows down to the inside of a balcony leader 70 provided to a downstairs column 41 downward of the column 51. For that purpose, even if the inner balcony is a long one lying across a plurality of sections, since the drainage flows from two balconies toward one column, the drainage can be efficiently made.