The purpose of this study is to analyze whether differences could be found in the data of speaking and writing tasks from Japanese language learners. Interlanguage variability found in such tasks has been studied since the '70s. Tarone (1983) asserts that the cause of variability that appears in tasks carried out simultaneously is the difference in attention occurring between them. The data used in this study are partially from the data of the Japanese Learners Corpus project that is currently being constructed. The corpus consists of Japanese language learners from five countries, namely 15 speakers each of Indonesian, English, Thai, Chinese and German, and a total of 75 people. There are no significant differences in Japanese language abilities among learners. Analysis of the narrative portions of this corpus reveals the following four usage patterns: (1) passive + modality shimatta, (inu ni tabemono o) taberareteshimaimashita/ taberareteshimatta, (2) passive taberaremashita, (3) tabeteshimaimashita and verb + modality teshimau, (4) usage of the simple past tense. Furthermore, an analysis was done based on the variability in the use of these patterns in speaking and writing tasks. When usage differed, the writing task contained more complex patterns than the speaking task, but half of the cases showed no difference in complexity. In addition, in the writing task, learners used complex patterns, but they made mistakes, or used simpler forms in order to avoid mistakes. Based on these results, we conclude that interlanguage variability is very closely related to learners' linguistic knowledge, metalinguistic knowledge, and psycholinguistic knowledge of the processes of the construction of meaning.