A trolley of a crane is arranged to move along a main support structure of the crane. The trolley includes a support frame structure; bearing wheels fastened to the support frame structure and by means of which the trolley is arranged to move along the main support structure; a hoisting mechanism that has a rope drum for a hoisting rope; a rope pulley arrangement through which the hoisting rope may be guided from the rope drum to a fixed fastening point on the trolley; and a hoisting member in cooperation with the hoisting rope for hoisting a load. The rope drum is supported to the support frame structure of the trolley so that the axle of the rope drum is parallel to the main support structure. The rope pulley arrangement is located, in the axial direction of the rope drum, at least partly outside one rope drum end which is on the side of said fastening point. The support frame structure is divided into two separate frame parts, whereby the first frame part supports the rope pulley arrangement and the rope drum end on the side thereof, and whereby the second frame part supports the opposite end of the rope drum.