An apparatus for producing diesel fuel and jet fuel using Fischer-Tropsch synthetic oil, the apparatus including a hydrofining reactor, a hot separator, a first rectifying column, a hydrocracking reactor, a hydroisomerization reactor, a second rectifying column, a first mixing chamber and a second mixing chamber. The hydrofining reactor includes a raw material inlet and a hydrofining product outlet. The hot separator includes a separated oil outlet and a hydrofining product inlet which is connected to the hydrofining product outlet. The first rectifying column includes a tail oil fraction outlet, a diesel fraction outlet and a separated oil inlet which is connected to the separated oil outlet. The first mixing chamber includes a circulating hydrogen inlet, a first mixture outlet and a tail oil fraction inlet which is connected to the tail oil fraction outlet.