A pneumatic tool comprising a casing unit having an air inlet passage, and an air motor mounted in said casing unit, and including a cylinder wall that surrounds a motor axis and that defines an air chamber, said cylinder wall has first and second passages (216, 218) that are in spatial communication with said air chamber, each of said first and second passages (216, 218) having an open end (2160, 2180) formed at an outer surface of said cylinder wall, characterized in that it comprises at least one sub-passage that is spatially connected to one of said first and second passages (216, 218), that is isolated from the other one of said first and second passages (216, 218), and that has an open end formed at said outer surface of said cylinder wall between said open ends (2160, 2180) of said first and second passages (216, 218), said open end of said at least one sub-passage being smaller than said open end (2160, 2180) of said one of said first and second passages (216, 218); and said pneumatic tool further comprises a rotary valve mounted to said air motor and rotatable about a valve axis, said rotary valve having an opening and an intermediate passage that intercommunicates said opening with said air inlet passage of said casing unit, and a turning unit movably mounted to said casing unit and connected to said rotary valve, such that movement of said turning unit relative to said casing unit drives said rotary valve to rotate about the valve axis relative to said air motor among a first-end position, where said opening is in spatial communication with said first passage, so that air traveling through said air inlet passage of said casing unit is allowed to flow into said air chamber of said air motor for driving operation of said air motor, a second-end position, where said opening is in spatial communication with said second passage, and at least one in-between position, where said opening is in spatial communication with said at least one sub-passage. a casing unit having an air inlet passage, and an air motor mounted in said casing unit, and including a cylinder wall that surrounds a motor axis and that defines an air chamber, said cylinder wall has first and second passages (216, 218) that are in spatial communication with said air chamber, each of said first and second passages (216, 218) having an open end (2160, 2180) formed at an outer surface of said cylinder wall, characterized in that it comprises at least one sub-passage that is spatially connected to one of said first and second passages (216, 218), that is isolated from the other one of said first and second passages (216, 218), and that has an open end formed at said outer surface of said cylinder wall between said open ends (2160, 2180) of said first and second passages (216, 218), said open end of said at least one sub-passage being smaller than said open end (2160, 2180) of said one of said first and second passages (216, 218); and first and second passages (216, 218) that are in spatial communication with said air chamber, each of said first and second passages (216, 218) having an open end (2160, 2180) formed at an outer surface of said cylinder wall, characterized in that it comprises at least one sub-passage that is spatially connected to one of said first and second passages (216, 218), that is isolated from the other one of said first and second passages (216, 218), and that has an open end formed at said outer surface of said cylinder wall between said open ends (2160, 2180) of said first and second passages (216, 218), said open end of said at least one sub-passage being smaller than said open end (2160, 2180) of said one of said first and second passages (216, 218); and said pneumatic tool further comprises a rotary valve mounted to said air motor and rotatable about a valve axis, said rotary valve having an opening and an intermediate passage that intercommunicates said opening with said air inlet passage of said casing unit, and a turning unit movably mounted to said casing unit and connected to said rotary valve, such that movement of said turning unit relative to said casing unit drives said rotary valve to rotate about the valve axis relative to said air motor among a first-end position, where said opening is in spatial communication with said first passage, so that air traveling through said air inlet passage of said casing unit is allowed to flow into said air chamber of said air motor for driving operation of said air motor, a second-end position, where said opening is in spatial communication with said second passage, and at least one in-between position, where said opening is in spatial communication with said at least one sub-passage. a rotary valve mounted to said air motor and rotatable about a valve axis, said rotary valve having an opening and an intermediate passage that intercommunicates said opening with said air inlet passage of said casing unit, and a turning unit movably mounted to said casing unit and connected to said rotary valve, such that movement of said turning unit relative to said casing unit drives said rotary valve to rotate about the valve axis relative to said air motor among a first-end position, where said opening is in spatial communication with said first passage, so that air traveling through said air inlet passage of said casing unit is allowed to flow into said air chamber of said air motor for driving operation of said air motor, a second-end position, where said opening is in spatial communication with said second passage, and at least one in-between position, where said opening is in spatial communication with said at least one sub-passage.