A track shoe connecting link 25 has shaft holes 31, 32 at both end portions. In the track shoe connecting link 25, a plurality of insertion holes 39 are formed between the shaft holes 31, 32, and window holes 40, 41 are formed so as to correspond to each insertion hole 39. A bolt 43 is inserted through each of the insertion holes 39 and a nut 44 is screwed onto a distal end of the bolt 43 in each of the window holes 40, 41. Accordingly, the track shoe connecting link 25 is fixed to a track shoe 26. The area of the window hole 41 that is adjacent to the second shaft hole 32 is greater than the area of the window hole 40. Accordingly, the rigidity of the track shoe connecting link 25 becomes smaller toward the second shaft hole 32.