PURPOSE: To prevent foreign materials from flowing downward by fixing a guide plate at the rotary part of the rake in the lower end of the front screen and positioning the upper end of the rear screen in the downstream side of the front screen at the higher level than the allowable highest position of the motion.

CONSTITUTION: A front screen 2 is installed in a water way 1 and a rear screen 3 is installed in the downstream of the front screen 2 in parallel with it and further, the upper end of the rear screen is positioned at a little higher level than the allowable highest position of its moving. Next, a rake 5 is arranged to be driven along the front and rear screen 2, 3 to move down in the back side with an endless chain 6. And a flat guide plate 4 made of a pipe or U-shaped pate is fixed at the rotary part of the rake in the lower end of the front screen 2. In this way, the foreign materials in the front and rear screens 2, 3 are prevented from clogging therein to operate smoothly and prevent a short circuit of water stream and hence, the foreign materials are prevented from flowing downward.