Fuel vapor treatment device

A fuel vapor treatment device is provided with: a shutoff valve (21) for opening and closing a fuel vapor passage (16) between a fuel tank (2) and a canister (3); a first purge control valve (23) for opening and closing a purge passage (19) between the canister (3) and the intake passage (17) of an internal combustion engine (1); and a second purge control valve (32) for opening and closing a tank opening passage (31) between the canister (3) and the fuel tank (2). When pressure is released for fuel filling operation, the second purge control valve (32) having a small diameter opens before the shutoff valve (21) opens, and gas blowing at the time of opening of the shutoff valve (21) is prevented. Whether or not the second purge control valve (32) is seized is diagnosed on the basis of the amount of pressure reduction after the second purge control valve (32) is opened. 蒸发燃料处理装置具有：封闭阀(21)，其对燃料箱(2)与吸附罐(3)之间的蒸发燃料通路(16)进行开闭；第1净化控制阀(23)，其对吸附罐(3)与内燃机(1)的进气通路(17)之间的净化通路(19)进行开闭；以及第2净化控制阀(32)，其对吸附罐(3)与燃料箱(2)之间的箱开放通路(