This study was undertaken to clarify the processes by which a spouse living together with his/her partner diagnosed as having intractable cancer carves a new role for himself/herself, and to explore ways to provide nursing support for such a spouse. Towards this end, we carried out semi-structured interviews of 13 spouses and analyzed the data by modified grounded theory approach (M-GTA). The initial step for the spouse was to understand the intractable nature of his/her partner's disease. Then, through "taking on the spouse's roles while believing that 'the sick partner is still OK' ", the spouse perceives a renewed sense of gratitude for the existence of the patient in his/her life. Thereafter, triggered by a "recognition of the patient's continuing to weaken", the perspective of the spouse changes markedly, followed by the role acquisition process and acquisition of the "new role formed through the processes of role substitution". The spouse undergoes growth through these processes. At the same time, he/she comes to vividly feel the "value of the patient's existence, deepened through the role substitution processes". Nurses should become involved at the appropriate time when the spouse begins to detect weakening of the patient and carry out continuous assessment to ensure that the spouse does not feel excessively burdened.