This study builds a theoretical model to examine how supply chain finance (SCF) services using fintech can ease e-commerce suppliers' capital constraints. Despite the innovation in the logistics industry during the Fourth Industrial Revolution and the increasing online shopping in the post-COVID era, small e-commerce enterprises may fail to grow owing to their budget constraints. Reverse factoring is believed to ease such suppliers' capital constraints. We analyze the effect of reverse factoring using the capital-constrained newsvendor model, and we consider the impacts of additional funding from SCF services. Our results show that SCF services reduce ecommerce suppliers' initial orders and, thus, alleviate their budget constraints. This finding suggests that the discount factor of reverse factoring should be higher to ease small suppliers' budget constraints and allow the e-commerce industry to grow sustainably.