Transcranial direct current stimulation (tDCS) is a relatively new non-invasive brain stimulation technique that can increase or decrease the excitability of a stimulated cortical region. This study investigated the effect of tDCS over the primary motor cortex (M1) on the motor learning task of the dominant hand. Eighteen healthy right-handed subjects (mean age 20.9, SD ±1.1, range 19-23) participated in this experiment. For the stimulation of the M1, the anodal, cathodal or sham (depending on the group assignment) electrode was placed over C3 (international 10/20 system). The reference electrode was placed above the right orbit. Subjects were instructed to perform a two-ball-rotation task for 30s with the right hand as fast as possible. Subjects underwent 12 trials with a 100s inter-trial intervals. Specifically, subjects firstly performed a trial without tDCS stimulation (pre-test). Subjects then performed 10 trials in which tDCS were continuously applied (training session). Finally, subjects performed a trial without tDCS stimulation to see learning effect (post-test). On each trial, the number of ball rotations was measured. There was no significant difference in the number of rotations at the pre-test among groups (F (2,15)=2.01, p>0.05). We defined the degree of motor learning as the skill measure (skill measure = the number of rotations at N trial / Pre-test). A two-way ANOVA with factors of stimulation type (anodal and cathodal) and trials (1-12 trials) revealed that the main effects of stimulation type (F (1,10)=4.99, p<0.05) and trials (F (11,110)=37.43, p<0.05) were significant; skill measure in the anodal group was higher than the cathodal group. The stimulation type × trials interaction was not significant (F (11,110)=1.86, p>0.05). A post-hoc t-test revealed that skill measure of the anodal group was significantly improved compared with the cathodal group at the post-test (t (10)=2.05, p<0.05). The sham group showed similar learning curve as the cathodal group but showed no significant difference with anodal group (t (10)=0.86, p>0.05). Our result showed that anodal tDCS over the primary motor cortex can enhance efficiency of motor learning of the dominant hand in healthy subjects.