A manual transmission for establishing one of multiple forward gear positions and a reverse gear position by combining a selection operation and a shift operation in response to a gear change request, the manual transmission comprising: a transmission case; a shift selection shaft supported by the transmission case, the shift selection shaft being configured such that i) the selection operation rotates the shift selection shaft around the axis of the shift selection shaft and ii) the shift operation displaces the shift selection shaft in an axis direction that the axis extends; a shift inner lever including a tubular portion and an arm portion, the tubular portion being integrally fitted to a radially outer side of the shift selection shaft, the arm portion being provided on a radially outer side of the tubular portion, and the arm portion extending outwardly in a radial direction of the tubular portion; an interlock plate including a boss portion and a projection, the boss portion being fitted to the radially outer side of the tubular portion such that i) the boss portion is displaced in the axis direction relative to the tubular portion of the shift inner lever and ii) the boss portion rotates integrally with the tubular portion around the axis, the projection being provided on a radially outer side of the boss portion such that the projection extends outwardly in the radial direction, and the projection having a slit such that the arm portion is inserted into the slit and the arm portion is displaced in the axis direction relative to the projection; a reverse lever provided integrally with the shift selection shaft; and a reverse shift arm supported by the transmission case via a bracket such that the reverse shift arm pivots relative to the transmission case, the reverse shift arm being configured to be pivoted by rotations of the reverse lever and the shift selection shaft along with the shift operation to the reverse gear position, and the bracket being provided with a regulation portion that regulates inclination of the interlock plate at a time when the shift operation is performed, characterized in that the transmission case includes a recessed portion; a part of the interlock plate is fitted to the recessed portion via a clearance that allows a relative displacement between the interlock plate and the transmission case; the recessed portion is configured to regulate the displacement of the interlock plate in the axis direction; and an inner wall (61a, 61b) of the recessed portion and the regulation portion are configured to receive a wall surface of the projection of the interlock plate to regulate the inclination of the interlock plate at a time when the shift operation to the forward gear positions is performed. a transmission case; a shift selection shaft supported by the transmission case, the shift selection shaft being configured such that i) the selection operation rotates the shift selection shaft around the axis of the shift selection shaft and ii) the shift operation displaces the shift selection shaft in an axis direction that the axis extends; a shift inner lever including a tubular portion and an arm portion, the tubular portion being integrally fitted to a radially outer side of the shift selection shaft, the arm portion being provided on a radially outer side of the tubular portion, and the arm portion extending outwardly in a radial direction of the tubular portion; an interlock plate including a boss portion and a projection, the boss portion being fitted to the radially outer side of the tubular portion such that i) the boss portion is displaced in the axis direction relative to the tubular portion of the shift inner lever and ii) the boss portion rotates integrally with the tubular portion around the axis, the projection being provided on a radially outer side of the boss portion such that the projection extends outwardly in the radial direction, and the projection having a slit such that the arm portion is inserted into the slit and the arm portion is displaced in the axis direction relative to the projection; a reverse lever provided integrally with the shift selection shaft; and a reverse shift arm supported by the transmission case via a bracket such that the reverse shift arm pivots relative to the transmission case, the reverse shift arm being configured to be pivoted by rotations of the reverse lever and the shift selection shaft along with the shift operation to the reverse gear position, and the bracket being provided with a regulation portion that regulates inclination of the interlock plate at a time when the shift operation is performed, characterized in that the transmission case includes a recessed portion; a part of the interlock plate is fitted to the recessed portion via a clearance that allows a relative displacement between the interlock plate and the transmission case; the recessed portion is configured to regulate the displacement of the interlock plate in the axis direction; and an inner wall (61a, 61b) of the recessed portion and the regulation portion are configured to receive a wall surface of the projection of the interlock plate to regulate the inclination of the interlock plate at a time when the shift operation to the forward gear positions is performed.