In an engine intake system, an air cleaner and downstream sides of throttle valves in throttle bodies provided in intake passages are connected by bypass passages. An idle speed control apparatus provided at a midpoint of the passage controls amounts of air supplied during an idling operation. End portions of the bypass passages connected to the throttle bodies are located in higher positions than end portions of the bypass passages connected to the air cleaner so that the bypass passages are inclined downward toward the air cleaner. As a result, water is prevented from blocking the bypass passages via a simple structure.