A dump truck is provided with a ground fault detection device that detects a ground fault detection voltage V0 as a difference between a detection voltage Vp between a positive electrode line of a DC bus and a neutral point N and a detection voltage Vn between the neutral point N and a negative electrode line of the DC bus and detects a ground fault based upon the ground fault detection voltage V0. The ground fault detection device includes a DC component determining section that extracts a DC component VLdc from the ground fault detection voltage V0 and determines a ground fault based upon the DC component VLdc, and a drive frequency component determining sections (that extract drive frequency components VLiR, VLiL of the inverters from the ground fault detection voltage V0 and determine a ground fault based upon the drive frequency components VLiR, VLiL.