An apparatus for continuously producing polyisocyanate is provided for quickly contacting polyamine and carbonyl chloride in order to suppress an undesirable reaction between polyamine and polyisocyanate so that a by-product can be reduced and the yield of polyisocyanate can be improved. In a circulatory line 7, a material-mixing portion 8, a high-shear pump 3, a reactor 4, a liquid-feeding pump 5 and a cooler 6 are interposed in series along the direction of the flow of a reaction solution, thereby forming a closed line. In this apparatus 1, after polyamine and carbonyl chloride are supplied in the material-mixing portion 8, the reaction solution is sheared by the high-shear pump 3 in a state where the contact of the polyamine with the reaction solution is minimized. Thus, the formation of a urea compound as a by-product can be suppressed and the yield of polyisocyanate can be improved.