The present study investigated the equivalent dipole sources of two types of human sleep spindles (14 and 12Hz) during stage 2 sleep. Dipole analysis of the 21 scalp EEGs (Fp1,Fp2,F3,F4,C3,C4,P3,P4,O1,O2,F7,F8,T3,T4,T5,T6,Fpz, Fz, Cz, Pz and Oz) was carried out on ten male subjects (20-26yr). This study showed that sleep spindle can be represented by single equivalent dipole. For both 14 and 12Hz sleep spindles, the equivalent dipole sources appeared in center of the brain. The orientation of the equivalent dipole of 14Hz sleep spindle was in the centro-parietal direction, while that of 12Hz sleep spindle was in the frontal direction. These results suggest that both types of sleep spindle activities are generated in the thalamus, and the thalamo-cortical pathway are different for the two types of sleep spindles.