A valve train includes a primary rocker arm 50 oscillating about a primary oscillating center line L4 in response to the rotation of an inlet cam 21, a secondary rocker arm 60 oscillating about a secondary oscillating center line L5 so as to transmit a valve drive force via the primary rocker arm 50 to the inlet valve 14 and a holder 30 which supports the primary and secondary rocker arms 50, 60 in an oscillatory fashion in such a manner that the primary and secondary oscillating center lines L4, L5 oscillate together. A cam profile 55 has a lost motion profile 55a a drive profile 55b are formed on an abutment portion 54 of the primary rocker arm 50. A sectional shape of the lost motion profile 55a is an arc-like shape which is formed about the primary oscillating center line L4.