Classical and quantum dynamics for an extended free rigid body (拡張自由剛体の古典および量子力学) In this paper, an extended free rigid body of dimension three is defin ed and analysed both in classical and quantum mechanics. The inverse inertia tensor, which is a positive-definite symmetric matrix in the ordinary case, is generalized to arbitrary symmetric ones in our case. With an arbitrary symmetric matrix chosen, associated is a Lie-Poisson structure on the Euclidean space of dimension three, through which the classical dynamics for an extended free rigid body is analysed by means of two characteristic first integrals. Further, the flows on the energy surfaces, their fixed points, and their stabili ty are studied. In parrallel with this, the quantum dynamics is formulated as the problem of the simultaneous spectral resolution of the two operators which are viewed as the q uantization of the first integrals in the classical dynamics of the extended fre e rigid body. The explicit spectral resolution are obtained, when the extended rigid body is a n extended symmetric top.