The mechanism of psychotherapy is explained by the recent developments in neuroscience and neuroimaging. The purpose of this study is to understand the nature of psychotherapy and to discuss the future of psychotherapy improvement with the help of advances of the neurobiological findings in psychotherapy. For this study, we investigated a wide range of materials. We searched for various researches on psychotherapy, brain, and neurobiology. In addition to the conventional psychodynamic psychotherapy, we investigated research findings on cognitive behavioral therapy, interpersonal psychotherapy and eye movement desensitization and reprocessing (EMDR). Moreover, based on the actual experiences of treating patients, we speculated the neurobiological mechanisms of the process and results of psychotherapy. With the development of neuroscience, we are now able to understand the personal consciousness, unconsciousness and developmental process. Also subdividing the disease is made possible. Personalized treatment has become available, and we are able to predict the prognosis of patients. Our memories are composed by implicit memory and explicit memory. By psychotherapy, we can consciously remember explicit memory, and it becomes easier to explore implicit memory through free association. Through psychotherapy, we will also be able to learn the effect of acquired environment and experience. Psychotherapy is able to correct human behaviors by modifying the memories. Through the regulation of emotions, it becomes possible to modify the memories and correct the behaviors. In this process, doctor-patient relationship is the main factor which cause positive treatment effects. Furthermore imagination therapy or unconscious, non-verbal stimuli could bring about positive treatment effects. Now psychotherapy could be explained and studied by neuroscientific researches. In this sense, we could provide the direction of future advances in neuroscience by the neurobiological understanding of psychotherapy.