To provide bit arrangement which drastically reduces the abrasion and damage of bits of an excavator, and improves the cost efficiency and working efficiency of the excavator.

According to the bit arrangement, 16 bits 2d, a groove central bit 2d", and 12 groove lateral edge bits 2d' for excavating groove lateral edges, are fixed to 10 mounting plates 2c. The bits 2d, 2d", 2d' are each shaped like the vee. The bits 2d' include those which are located at the lateral edges of the plate and those which are fixed to the plate diagonally with respect to a traveling direction and protruded from the lateral edges of the plate. The bits 2d', 2d" are higher in height than the other bits 2d and more protruded than the other bits, and both the lateral edges and the central portion of the groove are firstly excavated as shown by the two-dot chain line, whereby excavated portions function as free faces. In this manner, the free faces are first formed on both sides and the central portion of the groove and then the other portions are excavated by the other bits 2d, which leads to easy excavation of the groove, to thereby reduce the abrasion of all the bits.