This study aims to investigate ChatGPT's ability to comprehend input from nonnative speakers, specifically those learning English as a second language, with Japanese speakers serving as the model population. The experiment examines how ChatGPT evaluates the difficulty levels of the Test of English for International Communication (TOEIC), which is widely taken by nonnative English speakers of varying proficiency levels. This study also measures ChatGPT's response to discourses produced by nonnative speakers--one containing grammatical errors and the other incorporating sociolinguistic or strategic competence expressions. The findings indicate that ChatGPT demonstrates proficiency in lexical and grammatical features and can comprehend nonperfect grammatical discourses produced by nonnative speakers. However, ChatGPT does not accurately perceive the varying degrees of difficulty experienced by nonnative speakers. Moreover, while ChatGPT can comprehend sociolinguistic expressions when the context is clear, its understanding of other communication strategies employed by nonnative speakers is relatively limited.