The size of E-commerce market in Japan continues to grow, particularly, for Fast Moving Consumer Goods (FMCG). The aim of this study is to understand online channel use behavior, assuming that the growth of a consumers' online channel use continues. The authors proposed a Latent Growth Model to estimate the online purchase incidences (purchase or non-purchase) in FMCG. As a result, the authors identified consumer characteristics that the consumers who are likely to purchase online have a lot of time, make bulk purchases and the consumers whose online purchasing increase are time-constrained for shopping, make purchases in holidays, have high price sensitivity. It is also suggested that understanding purchase characteristics (not demographics) is important in a longitudinal perspective. Furthermore, online purchasing in FMCG has strongly influenced the experiences of the usage of EC website on PCs compared with mobile. However, the authors also suggested that the influence of mobile is increasing by consumers gaining experience over time.