An improved porous bearing and a motor which is provided with the porous bearing in which the friction losses and reflection of shaft are reduced, noises caused by the vibrations are avoided with low cogging or low jitter, and in addition, the manufacturing process is simplified to obtain long-life products at low cost. The number (C) of grooves of the porous bearing meets at least one of the following equations: nA+mB-C.noteq.0, nA-C.noteq.0 and mB-C.noteq.0 wherein A is the number of magnetic poles of the motor magnet, B is the number of the slots of the armature, and n and m are integers, respectively.