Background: The degree of difficulty of skills of paretic upper limbs in daily life has not been investigated. Objective: To determine the internal validity and level of difficulty of items of the Functional Skills Measure After Paralysis (FSMAP), which can be used to evaluate the functional skills of daily living for stroke patients. Method: A total of 105 first-stroke patients were assessed using the FSMAP. The evaluation system consists of 65 items in 15 categories. We examined the internal validity and level of difficulty of these items using Rasch analysis. In this study, an item with either infit or outfit of >= 1.5 was defined as underfit. Results: Rasch analysis showed that 8 items were underfit. The highest infit and outfit logits were 2.47 for "Trouser donning/doffing" and 8.44 for "Paper manipulation". "Shirt donning/doffing" was the easiest item and "Coin manipulation" was the most difficult, with difficulty logits of -35.8 and 41.5, respectively. Conclusion: The therapist can confirm items that the patient can or cannot perform. By understanding the level of difficulty of each item, the most appropriate functional skill to focus on acquiring next can be identified.