Minitracheotomy is a useful procedure for the respiratory management of patients with sputum retention observed frequently in chronic lung disease and postoperative respiratory failure. However, we experienced a case of hypercapnea after minitracheotomy. An 83-year-old woman was scheduled for gastrectomy. She had respiratory failure of Hugh-Jones 5 with fibroid lungs and the infection with atypical Mycobacterium and MRSA. Her sputum was adhesive and showed persistent increase during pre- and intra-operative periods. After the operation, minitracheotomy was carried out against the sputum retention by using Portex Mini-Trach II kit. Hypercapnea, however, was observed in spite of no evidence of the surgical complications such as bleeding or inadequate care for sputum from the inserted tube. Bronchofiberscope revealed adhesive sputum stuck to the space between the inserted tube and the trachea. In this case, hypercapnea was improved by opening the top of the inserted tube and frequent care for sputum. In cases with a large amount of adhesive sputum, sputum retention may easily occur not only at the peripheral bronchial branch but also between the inserted tube and the trachea and it can cause hypercapnea which may be overlooked.