An intake device of an engine comprises an intake manifold of a four-cylinder inline engine and a water-cooling type of intercooler. The intake manifold includes a downstream branch pipe portion connecting to cylinders, a chamber portion connecting to the downstream branch pipe portion, and an upstream intake pipe portion connecting to the chamber portion. A rectangular opening portion having a vertically-long shape is formed at the upstream intake pipe portion. The intercooler includes an intercooler body portion having a pair of faces which has the widest face-area and faces to each other in an engine width direction. The intercooler body portion is installed in the chamber portion, by being inserted through the rectangular opening portion, so as to divide an inside of the chamber portion into two parts in the engine width direction thereby.