Abstract: A pebble-stone crushing device for use in an excavator for laying pipelines underground has a plurality of rotor teeth formed integrally with the rear face of a cutter head which is mounted in the most front part of an excavator body to excavate a working face in front thereof, and a plurality of stator teeth formed radially on and integrally with an annular front face plate of said excavator body so as to cooperate with said rotor teeth. The stator teeth comprises plural groups of radially spaced apart tooth members having different length. Further, the tooth members comprises groups of comparatively long main tooth members and groups of comparatively short auxiliary tooth members each being disposed, respectively, between every adjacent two main tooth members.