To provide a box culvert into which high chemical prestress can stably be introduced and which demonstrates such flexural strength as to sufficiently endure the load of external pressure and ensures water tightness, and to provide a manufacturing method to obtain such box culvert easily.

The box culvert is a molded product of a concrete containing (A) a clinker pulverent having, as the effective component, calcined lime particles in which those of ≤90 μm in diameter make ≥90 wt% or free calcined lime, (B) a substance having the pozzolanic reactivity, (C) a water reducing agent, (D) cement and (E) aggregate. The inner surface of the molded product is formed with a polymer resin.