PURPOSE: To improve the constructing performance and economical efficiency of a form body for the construction of a concrete structure.

CONSTITUTION: In a form body with vertical batter members and lateral batter members connected in grated shape to fit a sheathing board, the lateral batter members 2a-2c disposed between the vertical batter members 1, 1 are connected being different in the length protruding from the vertical batter member 1. The sheathing board 3 is thereby formed bulging arcuately onto the concrete side. As a result of the form body bending outward by the pressure caused by the placing of concrete, the sheathing board 3 is made a plane.