A cart has an assistant stand mechanism, which includes two first casters, a pair of metallic angle plates, a support rod, and a second caster with a brake; each of the first casters is fitted to one of two rear lateral straight parts of a chassis; the metallic angle plates are each screwed onto a respective one of the rear lateral straight parts of the chassis; the support rod is secured to the metallic angle plates at two ends such that it crosses the cart, and is normally perpendicular to the ground where the cart stands; the second caster is fitted to the support rod; further, there are two sloping rods, each connected to the support rod at one end, and connected to a corresponding metallic angle plate at the other end; thus, the cart can stand on the casters with the chassis in upright position.