This study is a multicenter, double-blind, randomized, and confirmed clinical trial in patients taking antidepressants during the 6-week stimulation period , sham stimulation group, low real stimulation group (1mA), high real stimulation group (2mA) and treatment every day for 6 weeks (a total of 42 times). As a primary outcome, the investigator analyze the improvement effect of working memory ability, and confirm whether the effects of anxiety and depression are improved by the secondary outcome, together with the quality of life evaluation.

During the clinical trial period, a total of 4 to 5 outpatient visits are made, and changes are evaluated through neuropsychological examination by visiting at 2, 4 and 6 weeks based on the baseline time point. In addition, in the case of patients who agree after 6 weeks of participation, an additional 6 weeks of high real stimulation is used to conduct an open extension study.

Inclusion Criteria:

1. Diagnosis of major depressive disorder
2. CGI severity (severity of Illness) score of 3 or higher
3. Patients receiving medication for depression at the time of study participation
4. Those who can read and understand the subject's explanation and consent form and who can respond to questionnaires

Exclusion Criteria:

1. History of clinically significant medical neurological disease or history of head injury
2. In case of mental retardation or cognitive impairment enough to affect the writing of consent form or conducting research
3. Severe suicidal risk or psychotic symptoms determined by the clinician
4. In the case of a contraindication to the implementation of tDCS (when a metallic auxiliary tool is inserted in the head)
5. Those who are judged to have problems with the attachment of EEG and DC stimulation electrodes due to deformities, inflammatory reactions, or other dermatological problems at the electrode attachment site
6. Among female subjects who are likely to become pregnant, those who do not agree to contraception by a medically acceptable method for up to 24 weeks after application of the investigational medical device in this clinical trial
7. Pregnant women
8. Any other person who has reasons to judge that the investigator is unsuitable for participation in the clinical trial