PURPOSE: To open the exhaust valve of a cylinder close to the start of a compression stroke from the end of an intake stroke to enable an exhaust brake to act by adding oil passages in mechanism for actuating master pistons by locker arms actuated by push rods to generate pressure to oil and actuating the exhaust valve to open by the generated oil pressure through slave pistons.

CONSTITUTION: Oil passages 11A-11C, 12A-12C are provided in such a way that pressure is generated to oil supplied to the oil passages by actuating master pistons 2A-2C by locker arms actuated by the push rods of other cylinders at the operating time of an exhaust brake and that one of two exhaust valves 8a, 8b of the cylinder close to the start of a compression stroke from the end of an intake stroke is opened by the generated oil pressure through slave pistons E1, E2.