A tool box includes a left cover and a right cover which are pivotably connected on the left sidewall and the right sidewall respectively. The left cover, the right cover, the left sidewall and the right sidewall each have grooves defined in an inside thereof so that a first layer and a second layer connected by two rods are movably received between the left cover, the right cover, the left sidewall and the right sidewall by engaging protrusions on the first layer and the second layer in the grooves. The grooves each have two recesses defined in an inside thereof so that the protrusions can be shifted into the recesses to set the first layer and the second layer in position. Casters are connected to an under side of the tool box and allow the tool box to be moved in a convenient way.