The present invention relates to a reaction or separation device, wherein the materials circularly flow in a container and a pipe. Said device contains a container and an external circular pipe, wherein the container is a double-chamber structure. The inner chamber consists of an outer cylinder and an inner cylinder with the latter being jacketed by the former, and there is a space between the walls of the outer cylinder and the inner cylinder. The lower end of the outer cylinder is open and higher than the bottom of the container, and the outer cylinder is fixed to the wall or bottom of the container. The upper end of the inner cylinder is open and its lower end connects with the external circular pipe through the feed outlet. A continuous passage is sequentially formed from the spaces between the wall of the outer cylinder and that of the container, between the lower end of the outer cylinder and the bottom of the container, between the wall of the outer cylinder and that of the inner cylinder, and in the inner cylinder. The external circular pipe connects with the bottom of the container and leads to the inner chamber, and connects with the sidewall at the lower part of the container and leads to the outer chamber, respectively. The present invention also relates to a continuous esterification process, which comprises feeding liquid reaction materials to the reaction device and carrying out reaction under reaction conditions.