In an outboard motor having an engine and an engine cover adapted to cover the engine, the engine having an air intake passage that opens at the engine cover, it is configured such that a secondary air passage having an inlet disposed at an internal space of the engine cover and an outlet connected to the air intake passage at a position downstream of a throttle valve of the engine. The inlet of the secondary air passage is disposed at an internal space of the engine cover and near a belt cover that covers a timing belt adapted to transmit rotation of a crankshaft of the engine to a cam shaft of the engine.