This study investigated the effects of transcranial direct current stimulation (tDCS) on electroencephalogram (EEG) activity. 10 participants underwent EEG recording before, during, and after tDCS applied to the left dorsolateral prefrontal cortex. Analysis found that beta frequency power in the EEG significantly increased during stimulation and remained elevated after. This suggests tDCS may enhance cognitive functioning by increasing beta frequency activity in the brain. No significant changes were observed in other frequency bands. This is the first study to systematically analyze pre-, during-, and post-stimulation EEG data concurrent with tDCS.