A kneading apparatus having a kneading unit made up of a plurality of segment parts detachably mounted on a shaft disposed in the barrel includes a first segment part having a first length L1 related to an outer diameter D, a second segment part having a second length L2 shorter than the first length L1, and a third segment part having a third length L3 longer than the first length L1; the first length L1 is [the outer diameter D×a coefficient a]; the second length L2 is [the first length L1/a coefficient b]; the third length L3 is [the first length L1×the coefficient b]; the third length L3 is [L1+L2]; and the kneading unit has a segment pattern made up of a plurality of segment parts and mounted on the shaft interchangeably with another segment pattern.