Light irradiation is a promising way for spatial gel formation, and it is useful in cell arrangement by control of the shape of gels. To form the shape of gels by light irradiation, temperature control and irradiation of ultraviolet light, which causes damage to cells, are required. In this study, we propose a shape control method of DNA hydrogels by photodecomposition with visible light. By design of DNA sequences and modification of molecules, DNA hydrogels can be decomposed by changing the environment including temperature, pH, and the presence of specific molecules. In our method, the DNA hydrogels are constructed by self-assembly of Y-motif DNAs (Y-DNAs) combined with linker DNAs (L-DNAs). For optical control, the L-DNA is modified with quenchers. When quenchers are optically excited, thermal energy is released via a non-radiative relaxation process of the quenchers, and then denaturation of DNAs consisting of Y-DNAs and L-DNAs is induced. Separated Y-DNAs bind with a Cap-DNA which prevents Y-DNAs from recombination with L-DNAs, and DNA hydrogels are decomposed as a result of the separation of Y-DNAs and L-DNAs. This decomposition is only induced within the irradiation area. Thus, the shape is changed by control of light distribution. In experiments, we demonstrated the decomposition of DNA hydrogels according to holographically generated light patterns. This result shows that the shape of DNA hydrogels can be controlled by visible-light irradiation without changing the environment.