Methods: In this study, five subjects with colorectal cancer undergoing adjuvant chemotherapy were interviewed in-depth using the Giorgi study method. The contents of the nutrition education visits and in-depth interviews were transcribed in the language of the subject after recording, and the appropriateness of the data was improved by reflecting the subject’s actions and facial expressions. Results: After conducting the in-depth interviews for each subject, the experience of the subject’s diet and adjuvant chemotherapy was drawn into two domains, six elements, and 26 sub-elements. In the cognitive domain, the patients experienced physical and psychological changes, and the need for nutrition management was recognized by analyzing the dietary causes of the diseases. In the domain of practice, a knowing-doing gap was formed, unlike the patient’s will. Factors that inhibited compliance with nutritional management included digestive problems, sensory changes, loss of appetite, and social interaction stress. Conclusions Dietary management is very important for patients receiving periodic anticancer therapy, and step-by-step training and personal monitoring based on the chemotherapy order is necessary to maintain the patient’s will and social and environmental support.