Provided is a novel production method with which it is possible to produce a heteromultimeric
protein such as a
bispecific antibody. A method for producing a heteromultimeric
protein according to the present invention comprises: a
complex formation step for forming a first complex of the two proteins by bringing the two proteins into contact with each other, the two proteins comprising a first
protein and a second protein, the first protein comprises a first binding tag, a first cleavage domain, and a first domain in this order from the N-terminal to the C-terminal, and the second protein comprises a first binding partner capable of binding to the first binding tag, a second cleavage domain, and a second domain in this order from the N-terminal to the C-terminal. The first protein and the second protein are capable of forming a
dimer by means of the binding between the first domain and the second domain, the first protein and the second protein are bound to the first binding partner by means of the first binding tag, and the first domain is bound to the second domain to form the first complex; and a generation step in which the first cleaved domain and the second cleaved domain in the first complex are cleaved to generate a heterodimer of the first domain and the second domain.