Abstract: The optogenetics approach uses a combination of genetic and optical methods to control the functions in specific cells of biological tissues. Since the control of neuronal activity by irradiating channelrhodopsin-2 with blue light was reported in 2005, the application of optogenetics in the field of oncology has been initiated. The antitumor mechanisms of optogenetics approach include controlling neuronal activity, antitumor immunity, altering intracellular ion levels, controlling cellular forces, modulating cellular signal transduction, regulating genetics and epigenetics, and discovering cancer drugs. Control of cancer using light will be light in cancer therapy.