To solve the problem that a drain is not embedded in a prescribed direction because the drain temporarily fixed to a floor form among forms for forming a concrete floor is turned on a spacer when concrete is placed.

The drain 10 which is temporarily fixed to the floor form F among the forms for forming floors of a rooftop, a balcony, etc. of a building from concrete is held in a prescribed position by a holding device 30. The holding device includes a screw member 31 which is attached to an undersurface of a catch pan 11 of the drain 10 toward the floor form F, and a holding member 32 which is attached by being screwed to a lower end of the screw member 31 and abuts on the floor form F. A lower end surface of the holding member 32 has a rod-like protrusion 33 capable of being engaged with a through-hole Fa formed at the floor form F, and the holding member 32 can be separated when the concrete is solidified.