In a circuit device having a circuit element housed in a case, a rise of air pressure and occurrence of condensation in the case are prevented. A circuit device of the present invention includes a case formed of a bottom part and a side part, and a cover part covering an upper surface of the side part. In an internal space of the case, a circuit element such as a semiconductor element is housed. In a bottom part of the case, a land and leads are buried. A communicating part which causes the internal space of the case to communicate with an outside of the case is provided in the land. By providing the communicating part, the rise of air pressure and occurrence of condensation in the internal space due to change in temperature are suppressed. Furthermore, in the land made of metal, the communicating part can be easily formed by etching or the like.