The present disclosure relates to an arc extinguishing chamber base of a molded case circuit breaker and, more specifically, to an arc extinguishing chamber base of a molded case circuit breaker, manufactured using a thermoplastic resin. The present disclosure enables an arc extinguishing chamber base for forming a molded case circuit breaker to be manufactured using an aromatic polyamide-based thermoplastic resin, thereby enabling an increase in productivity, a decrease in component weight, a reduction in component production time, an eco-friendly effect, and recycling. Furthermore, component lifespan increases.