PURPOSE: To enable raking up of sunk sand and screen sediment, by a method wherein a frame, around which an endless chain is run, is vertically rockably secured to a truck travelling along a channel, rakes are mounted to the chain, and each of buckets is attached to each of the rakes.

CONSTITUTION: A travelling truck 7 reciprocatively travels on rails 6 installed along a channel 1. The upper end of a frame 9 is rockably secured to the travelling truck 7, and the forward end of the frame is elevated inside and outside the channel. Further, an endless chain 16 is run around the frame 9, and the chain 16 is provided with rakes 17. The rake 17 is provided with a bucket 18. This enables raking up of sunk sand and screen sediment of a coarse and a fine mesh screen.