A three-dimensional built-up toy includes a doll, a coupling element, a plurality of clothes, and a base all in the form of flat pieces. The doll piece is provided at one side near a middle portion with a first slit having a predetermined depth for engaging with a second slit provided on one side of the coupling element, so that the coupling element is perpendicularly connected to the doll. The base is provided with a plurality of insertion slots, any of which is adapted to receive a lower connecting edge of the doll, so that the doll could stand on the base. Each of the pieces of clothes is provided at one side with a third slit for engaging with the coupling element and thereby being changeably attached to the doll via the coupling element at any time as desired.