One aspect of the present invention is a drain pipe for a farmland, comprising a pipe body (30) having a flow channel of which the cross sectional area becomes larger at an end portion (32) thereof than at a starting portion (31) thereof, and having a support plate (33) that extends from one side thereof and water conveyance means (40) arranged on at least one side of the pipe body (30) to absorb water. Another aspect of the present invention is a method for constructing an agricultural waterway (22) having a bank (21) between farmlands (10) using the pipe body (30), comprising a first step of excavating the center of the bank (21) to construct the agricultural waterway (22) lower than the farmlands (10) a second step of placing the pipe body (30) on the agricultural waterway (22) and filling at least the space formed at the side surface of the pipe body (30) and a third step of installing drainage pipes (24) in the bank (21) to adjust the water level of the farmlands (10). Thus, the water level of the farmland can be held constant such that the water level of the farmland may not be higher than a predetermined level even upon occurrence of localized heavy rain caused by irregular and various meteorological changes, thus preventing damage to the crop caused by flooding and contributing to the improvement of agricultural productivity.Un aspect de la présente invention est un tuyau de drainage pour des terres cultivées comprenant un corps de tuyau (30) avec un canal découlement dont laire de la section transversale devient plus grande à une partie extrémité (32) de celui-ci quà une partie origine (31) de celui-ci, et avec une plaque de support (33) qui sétend à partir dun côté de celui-ci et un moyen de transport deau (40) situé sur au moins un côté du corps de tuyau (30) pour absorber leau. Un autre aspect de la présente invention est une méthode de construction dune voie deau agricole (22), avec une berge (21) entre des terres cultivées (10) utilisant le corps de t
