As part of the study to investigate filter performance in the actual conditions, particle removal efficiency evaluation method of filters in isopropyl alcohol was developed. Three kinds of particles which exhibit each different charged state in the chemical, and the sizes of which are around 10 nm, were selected as test particles for the evaluation. Pall 10-nm-rated surface-modified PTFE membrane filter was evaluated with the particles. The result was compared with the removal efficiency in deionized water. Also, the effect of adsorption on the removal efficiency in the system was discussed.