A molecular vacuum pump comprising: a housing (2, 3) in which an inlet port and an outlet port are formed; a stator portion (60, 70) disposed on an inner side surface of the housing; a rotating shaft enclosed in the housing and supported rotatably; a rotor portion (8, 10) fixed to the rotating shaft; a first turbo molecular gas transfer mechanism that has rotor blades disposed radially from an outer circumferential surface of the rotor portion, and stator blades protruding from an inner side surface of the stator portion toward the rotating shaft, and transfers, to the outlet port, gas suctioned from the inlet port by an interaction between the rotor blades and the stator blades; and a second, thread groove gas transfer mechanism, that is disposed on the outlet port side of the first turbo molecular gas transfer mechanism, has a thread groove (61, 62) on either one of the opposing surfaces of the rotor portion and the stator portion, said second, thread groove gas transfer mechanism transfers, to the outlet port, the gas suctioned from the inlet port, and forms a radial clearance between thread groove peak surfaces, described as thread groove convex surfaces, formed in the thread groove and an opposing surface facing the thread groove convex surfaces, characterized in that the second thread groove gas transfer mechanism has a product contact avoidance structure (1000-1008; 1100-1102) in which: a portion of the radial clearance between the thread groove convex surfaces and the opposing surface facing the thread groove convex surfaces, during rotation of the rotor portion, is larger on the lower, outlet port side of the second thread groove gas transfer mechanism than on the upper, inlet port side of the second, thread groove gas transfer mechanism; and the portion of the radial clearance on the lower, outlet port side is larger than an amount of a deformation of the rotor portion by thermal expansion or creep phenomenon during rotation of the rotor portion, and in that in the second gas transfer mechanism, the product contact avoidance structure has a structure in which each of the thread groove convex surfaces, which are formed in a region of 1/2 of the second gas transfer mechanism in an axial direction, is cut from the outlet port side toward the inlet port side. a housing (2, 3) in which an inlet port and an outlet port are formed; a stator portion (60, 70) disposed on an inner side surface of the housing; a rotating shaft enclosed in the housing and supported rotatably; a rotor portion (8, 10) fixed to the rotating shaft; a first turbo molecular gas transfer mechanism that has rotor blades disposed radially from an outer circumferential surface of the rotor portion, and stator blades protruding from an inner side surface of the stator portion toward the rotating shaft, and transfers, to the outlet port, gas suctioned from the inlet port by an interaction between the rotor blades and the stator blades; and a second, thread groove gas transfer mechanism, that is disposed on the outlet port side of the first turbo molecular gas transfer mechanism, has a thread groove (61, 62) on either one of the opposing surfaces of the rotor portion and the stator portion, said second, thread groove gas transfer mechanism transfers, to the outlet port, the gas suctioned from the inlet port, and forms a radial clearance between thread groove peak surfaces, described as thread groove convex surfaces, formed in the thread groove and an opposing surface facing the thread groove convex surfaces, characterized in that the second thread groove gas transfer mechanism has a product contact avoidance structure (1000-1008; 1100-1102) in which: a portion of the radial clearance between the thread groove convex surfaces and the opposing surface facing the thread groove convex surfaces, during rotation of the rotor portion, is larger on the lower, outlet port side of the second thread groove gas transfer mechanism than on the upper, inlet port side of the second, thread groove gas transfer mechanism; and the portion of the radial clearance on the lower, outlet port side is larger than an amount of a deformation of the rotor portion by thermal expansion or creep phenomenon during rotation of the rotor portion, and in that in the second gas transfer mechanism, the product contact avoidance structure has a structure in which each of the thread groove convex surfaces, which are formed in a region of 1/2 of the second gas transfer mechanism in an axial direction, is cut from the outlet port side toward the inlet port side. a portion of the radial clearance between the thread groove convex surfaces and the opposing surface facing the thread groove convex surfaces, during rotation of the rotor portion, is larger on the lower, outlet port side of the second thread groove gas transfer mechanism than on the upper, inlet port side of the second, thread groove gas transfer mechanism; and the portion of the radial clearance on the lower, outlet port side is larger than an amount of a deformation of the rotor portion by thermal expansion or creep phenomenon during rotation of the rotor portion, and in that in the second gas transfer mechanism, the product contact avoidance structure has a structure in which each of the thread groove convex surfaces, which are formed in a region of 1/2 of the second gas transfer mechanism in an axial direction, is cut from the outlet port side toward the inlet port side.