A three-dimensional hydrogel scaffold of the present invention contains a cell to be transplanted in vivo and comprises a first hydrogel block on which a plurality of holes are formed and one or more second hydrogel blocks which are assembled to the holes and are biodegradable. A large hydrogel scaffold can be prepared by means of the assembly of the blocks. The survivability of the cell being transplanted is high and the biodegradability of the blocks varies, and thus the risk of hypoxia is reduced.