PURPOSE: To improve the effect of cooling an oil pan, etc. by a constitution wherein an opening letting the outside air flow to the rear of an engine is made in the part under the engine of an under cover which is arranged in extension from a front cross member to the under rear of the engine.

CONSTITUTION: An embossed part 21 is provided in the rear of the part under an engine 2 of an under cover C which is arranged in extension from a front cross member 1 to the under rear of the oil pan 4 of the engine 2. This embossed part 21 has a vertical wall 21a at the front end and a guide wall 21b continuing from the front end to the rear end. Moreover, an opening 22 is made in the vertical wall 21a of the embossed part 21 along the entire width of the wall 21a. While a car runs, part of an air stream T1 below the under cover C is led from said opening 22 into an engine room R, and simultaneously, an air stream T2 passing a radiator 3 is induced by said air stream T1 into the rear of the engine 2 through a space 10 between the oil pan 4 and the under cover C.