For the quantum mechanical three body problem with central potentials, separation of the rotational coordinates is performed systematically. We treat two particles in a symmeric way to apply Pauli princrple for the case of eidentical fermions. We construct a complete set of commuting observables, L^2, the total angular momentum, M, its z-component and N, the component around the normal through the third particle to the plane including three particles K_1, K_2 and N form three components of L in the body fixed moving frame. Single particle operators are expressed in compact forms by those operators. Thus, the separation procedure is simplified than hitherto known one. For the case of equal masses and L = O, a simple and symmetrical equation is derived.