The objective of the present invention is to reduce a meshing seal line length and further reduce a blowhole area. A compression side blowhole B2 is generated in a region surrounded by a male rotor side blowhole contour R1, a female rotor side blowhole contour R2, and a lower cusp line k2. By configuring a female rotor side blowhole contour R3 with a curve including at least two arcs C1 and C2, an area of the compression side blowhole B2 may be reduced. At a connection point between arcs, by making tangents of the arcs on both sides across the connection point to be the same gradient, the arcs may be smoothly connected.