The proliferation of cardiomyocytes is induced by expressing cyclin and CDK in the cardiomyocytes, and by suppressing the function or action of a Cip/Kip family protein or inhibiting the production of a Cip/Kip family protein. Among the Cip/Kip family proteins, it is preferable to suppress the function of p27 Kip1 or inhibiting the production thereof. As a recombinant vector to be used therefor, there is provided a vector comprising: (1) a cyclin gene； (2) a cyclin-dependent kinase gene； and (3) one or a plurality selected from the group consisting of a gene encoding a factor that inhibits the function or action of a Cip/Kip family protein and a nucleic acid sequence that inhibits the production of Cip/Kip family protein.
