The invention discloses a device for collecting garbage in a water body. The device comprises an arc-shaped base plate, multiple layers of baffles and a plurality of sub-plates, wherein the arc-shapedbase plate is fixed to a protection slope of the water body; the arc surface of the arc-shaped base plate are sunken towards the interior of the protective slope; the baffles are arranged at intervals in the length direction of the arc-shaped base plate; each baffle comprises a baffle body, and the baffle body is fixed to the arc-shaped base plate in the width direction of the arc-shaped base plate; the sub-plates are arranged at intervals, arranged on the corresponding baffle bodies in the vertical direction perpendicular to the corresponding baffle bodies and used for blocking garbage in the water body; the outer surface of each sub-plate is a wavy surface. Through verification of a large number of experiments, the inventor finds that the designed baffles meet the formula: D1/H=A*(C*D2/D1). Thus, the most garbage can be collected to maximum extent, and the garbage clearing cycle is greatly shortened. Moreover, the outer surfaces of the sub-plates are the wavy surfaces, so that the garbage is collected at the sub-plates more easily.