Objective : The purposes of this study were to compose items about the quality of life for family caregviers of people with dementia and to develop an instrument to assess the quality of life for the family caregiver of people with dementia by verifying its validity and reliability through Rasch analysis. Methods : Data were collected from families of people with dementia who got diagnosed with dementia from March 16, 2022, to November 4, 2022, and a set of 26 items that assess the quality of life for the family of people with dementia was used to collect data. SPSS 29.0 version was utilized to analyze general characteristics and exploratory factors of subjects the family of people with dementia. Rasch analysis was conducted through Winstep 3.80.1 to analyze construct validity and separation reliability of the quality of life for family caregiver of people with dementia. Results : In appropriateness analysis using Rasch analysis, 13 among 155 subjects were found to not fit, and 3 out of 26 items were also found to not fit. Items that demonstrated high difficulty were item 25 with a logit score of 1.07, item 20 with a logit score of 1.01, and item 6 with a logit score of 0.96 in that order. Items that demonstrated low difficulty were item 15 with a logit score of –2.13 and item 22 with a logit score of -0.92 in that order. Analysis of the rating scale indicated that the three-point scale was the most appropriate one. Analysis of separation reliability demonstrated that both subject and item separation reliability are high at 0.92 for subject separation reliability with a separation index of 3.47, and 0.97 for item separation reliability with a separation index of 5.87. Analysis of exploratory factors placed overall health, daily life, work and other activities, and pressure and stress at the bottom panel. Conclusion : The assessment instrument on quality of life for the family caregivers of people with dementia developed in this study is expected to be a tool for the family of people with dementia to assess their quality of life by themselves and to be a precursory guideline to prevent further decrease in quality of life.