The present invention relates to a switch molecule for activating a chimeric antigen receptor effector cell, to a polypeptide or fusion protein binding thereto, and to a chimeric antigen receptor. (i) When a switch molecule of the present invention is used, in order to improve safety of a CAR-T cell, if severe toxicity appears, a switch molecule lacking a targeting moiety can be injected to adjust activation of the CAR-T cell. (ii) When an antigen is mutated, or in order to cure various carcinomas, instead of an existing switch molecule, a switch molecule targeting a new antigen generated due to the mutation or a switch molecule targeting a different tumor associated antigen (TAA) can be injected into a patient to cure cancer more effectively.