PROBLEM TO BE SOLVED: To provide a simple and inexpensive switching operation structure of a threshing chamber of thresher capable of performing a maintenance work while preventing wrong operations by an operation of a fixing release lever of a lock member.SOLUTION: There is provided a threshing chamber switching operation structure comprising a threshing chamber case 3 supported as rotatable in the vertical direction using a fulcrum shaft 33 as a center of rotation, in setting the threshing chamber case 3 in threshing attitude by downward turning the threshing chamber case 3, disengageably fixing the threshing chamber case 3 to thresher lower machine casing 1a through a fixing mechanism 5, and releasing the fixing mechanism 5 with a releasing operation of a fixing releasing lever 3L in switching attitude from threshing attitude to maintenance attitude by upward turning of the threshing chamber case 3, the threshing chamber case 3 engages to a support locking mechanism 5b as capable of fixing in maintenance attitude, wherein in fixing the threshing chamber case 3 in maintenance attitude the fixing of the support locking mechanism 5b is set as freely releasable by an operation of the fixing releasing lever 3L.COPYRIGHT: (C)2014,JPO&INPIT【課題】ロック部材の固定解除レバーの操作によって、誤操作を防止したメンテナンス作業を行うと共に、簡潔で廉価な脱穀機の扱室開閉操作構造を提供する。【解決手段】扱室ケース3を機体奥側の支点軸33を回動支点として上下回動可能に支持し、扱室ケース3を下方回動させて脱穀作業姿勢にした状態で、脱穀下部機枠1aにロック機構5を介して係脱可能に固定すると共に、該ロック機構5を固定解除レバー3Lの操作により固定解除し、扱室ケース3を脱穀作業姿勢から上方回動させてメンテナンス作業姿勢にしたとき、該扱室ケース3を支持ロック機構5bに係合させてメンテナンス作業姿勢に固定可能に構成した脱穀機の扱室開閉操作構造であって、前記扱室ケース3をメンテナンス作業姿勢に固定しているとき、固定解除レバー3Lを操作することにより、支持ロック機構5bの固定を解除自在に構成した。【選択図】図3