An ignition plug cooling device of a vehicle engine for efficiently cooling the ignition plugs while increasing the freedom in the arrangement of the ignition plugs is provided. A vehicle engine includes a first ignition plug and a second ignition plug (29a, 29b) for making respective electrodes thereof face a combustion chamber (24) and are mounted on a cylinder head (3). An air flow passage (63) through which a flow of air passes and a cooling oil chamber (64) through which lubrication oil for the engine passes are formed in the cylinder head (3). The first ignition plug (29a) is arranged in the air flow passage (63) to enable a cooling of the first ignition plug (29a) by the flow of air which passes through the air flow passage (63). The second ignition plug (29b) is arranged adjacent to the cooling oil chamber (64) to enable a cooling of an area around the second ignition plug (29b) by oil which passes through the cooling oil chamber (64).