To provide a biaxial extruder excellently extruding with a simple constitution.

In the biaxial extruder, a pair of rotor shafts 1 is rotatably arranged such that the closer to the head end of the pair, the smaller the distance between the pair. The pair of rotor shafts 1 is respectively provided with screw blades 2 mounted on the head end side of the pair. The rotor shafts 1 are adapted such that one screw blade 2a enters gaps of the other screw blade 2b. Drive devices M for rotationally driving the pair of rotor shafts 1 are mounted on the respective base ends of the pair. The extruder has a screw blade contact prevention mechanism SS which, when the pair of rotor shafts 1 is driven, prevents the pair from having a phase difference greater than a predetermined level while allowing a predetermined phase difference at the pair of rotor shafts 1.