Mud and sand are prevented from entering between support-receiving members since both ends of the roller shaft are constructed so as to be held at both sides thereof when providing the upper roller on the travelling body frame secured in a civil engineering apparatus. The first and second support receiving members 19, 20 are constructed so that the members respectively support both end portions of the roller shaft 17a of the upper roller 17 on the upper part of the track frame 11 and cross frame 12 on the travelling body frame 10 secured at the lower part of the civil engineering apparatus, wherein the roller supporting portions 19a, 20b and a pair of coupling pieces 19a, 20a for coupling the roller supporting portions 19b, 20b to the travelling body frame 10 are formed to be substantially reverse U-shaped.