Play has been used as an intervention or evaluation tool for children. Developing a social play evaluation tool can provide clinical criteria for intervening in social play. We aimed to develop a social play evaluation tool for preschool children based on Parten’s stages of development. We tested the construct validity of the scale using confirmatory factor analysis and Rasch analysis, and the known-groups validity by examining the Rasch-calibrated mean score differences across age groups. A total of 40 preliminary items—17 items for associative play and 23 items for cooperative play—were examined. There were significant differences in the scores for associative play between ages 3 and 6 (F = 2.65, p = 0.049), and for cooperative play between ages 3 and 5, 3 and 6, and 4 and 6 (F = 10.44, p < 0.0001). The findings could contribute to subsequent development and validation of occupational therapy programs on play.