An environmental test apparatus is disclosed. The environmental test apparatus is configured to simulate the environmental variation in temperature and humidity. The environmental test apparatus comprises a box, a plurality of openings, a plurality of fans, two guiding elements and a plurality of controllers. The box has a plurality of sidewalls and a plurality of corners each being defined by three of the adjacent sidewalls, wherein the openings are disposed on at least two sidewalls of the box, and each of the fans is correspondingly disposed in each of the openings. The two guiding elements are disposed on two opposite corners for guiding the airflow in the hollow box, wherein the two opposite corners share a single sidewall. The controllers are configured to control the rotational speed of each fan and adapted to uniform the distribution of the temperature and the humidity inside the box.