To provide a noise reduction structure of a road sweeper capable of inexpensively constructing an engine room by a simple configuration and reducing noise.

An engine 5 for work for driving a blower 6 is stored in the engine room 25 on a chassis 2. The blower 6 exhausts an air stream into the outside air from an air exhaust part 21 through a communicating box-shaped noise reduction device 23. The engine room 25 is constituted by assembling a support column 32 and left and right members in a frame and attaching a hopper front side part front wall 31 as left and right side covers 27, 28, a front cover 26, and a rear cover and the noise reduction device 23 as an upper cover. The noise reduction device 23 is used also as the upper cover to reduce amount of used materials and provide the noise reduction structure inexpensively by the simple configuration. The noise reduction means 23 covers the whole upper part to reduce upper noise.