To provide a crushing apparatus which attains an increase in the crushing capacity with simple and inexpensive structure.

The crushing apparatus 13 for crushing the crushing object in fluid is provided with a hollow disk-like crushing vessel 20 formed with an annular flow path therein and opened at the lower face, and a pair of nozzles 30, 30 jetting fluid roughly along a tangential line of the annular flow path on the annular flow path, and disposed so that the jetted fluid collides countercurrently to each other. A rubber nozzle is adopted as the nozzle 30. The sludge treatment system 10 is provided with a solubilization tank 12 solubilizing activated sludge, the crushing apparatus 13 for crushing cell walls of the solubilized activated sludge, a neutralization tank 14 neutralizing the activated sludge, and a settling tank 17 settling and separating the sludge.