TRAP FOR DRAINAGE

A drain train is provided to prevent overflow of drain water, and foul smell and pests from coming over the drain trap by inserting a sealing plate inside an outer housing to shut off an end part of a guide pipe of an inner housing securely after discharge of the drain water. A drain trap having a space part(32) where the drain water collects drains a predetermined volume of drain water through a drain passage when the drain water overflows. The drain trap comprises a cover(10) having plural drain holes(10a), a main body(20) installed on the floor and having an engaging protrusion(21) on which the cover is placed, a hollow passage in the middle, an outer housing having an circular rim(31) for placing on the main frame and plural predetermined sizes of draining holes(33) on the sides, an inner housing having a body(40a) comprising integrated engaging pieces(41) hung on the inner upper part of the outer housing and an integrated guide pipe(42), and a sealing plate(50) inserted into the outer housing to open and shut the end part of the guide pipe of the inner housing.