A multifunction dumbbell includes a handle having two projections on both ends respectively; two hollow weight members each having a protrusion extending toward the handle; two spacer sleeves each having a closed flange fixedly secured to a joining portion of the handle and either projection, with the spacer sleeves fixedly fastened between the protrusions and the projections; two rings each having an inner diameter less than an outer diameter of the weight member so that the rings can be put on the weight members and retained thereon respectively; two half-spherical members each fixedly secured to the ring and complimentarily engaged with the weight member; and two truncated conic springs each put on the protrusion and a portion of the weight member to be retained between the spacer sleeve and the ring. The rings and the half-spherical members together are adapted to rotate about the weight members.