There is provided an intake apparatus of an engine for an outboard motor. An intake manifold, a throttle body and an intake silencer box are arranged at one of right and left sides of an engine block which is configured such that an axial direction of a cylinder coincides with a front and rear direction of the outboard motor. An intake duct communicating with an intake introduction port provided at an upper part of an engine cover is coupled to an upstream end of the intake silencer box. A first water separation part is arranged between the intake introduction port and the intake duct. A second water separation part is provided below a duct part of the intake duct. The second water separation part is formed by providing a drain hole at a bottom part of a resonator chamber part communicating with the duct part to reduce an intake noise.