The present disclosure relates to, inter alia, a gene for increasing biomass production isolated from Arabidopsis thaliana, and a method for producing a transgenic plant by using the same. More specifically, the present disclosure provides, inter alia, a composition for increasing production of plant biomass, a recombinant expression vector and a transgenic plant, comprising a base sequence encoding for the amino acid sequence of sequence number 2. Consequently, by using the gene for increasing biomass production of the present disclosure, it is possible to obtain a transgenic plant with which the amount of biomass production is increased and, ultimately, by using the same, it can be expected to be possible to increase starting materials for the pulp and papermaking industries, and starting materials for bioethanol.