A genetic recombinant human thrombin is provided. Human thrombin is efficiently prepared by the genetic engineering technique comprising the steps: (1) culturing a transfectant animal cell transfected with an expression vector in which a gene encoding human prethrombin is incorporated to the downstream of a promoter so as to produce and accumulate prethrombin in culture supernatant and recovering the produced human prethrombin; (2) treating a solution containing human prethrombin recovered in step (1) with ecarin so as to convert human prethrombin into human thrombin; and (3) purifying the solution obtained after the above activation process to obtain purified human thrombin. The present invention allows for provision of human thrombin in a large scale in a safe and economical manner due to exclusion of blood-derived components.