To easily and surely crush excavated material by using a simple crusher.

Inside a vertical cylindrical body 2 provided successively to the lower part of a hopper 1, an upper material bearing plate 4 having a crushed material passing opening 3 and a flat upper surface is fixed. Above the upper material supporting plate 4, a feeder 5 is provided for feeding excavated material to the excavated material passing opening 3. Below the upper material supporting plate 4, lower material bearing plates 7 rotated around the vertical shaft by a driver 6 leaving a space in parallel to the plate 4 are freely rotatably installed, and between the upper material bearing plate 4 and the lower material bearing plates 7, rotary crushing members 9 rotated by crushing member drivers 8 are provided on the vertical cylindrical body 2 movably in the inside and outside directions of the vertical cylindrical body 2 via the axis supporting means.