To achieve an electropneumatic converter with high maintainability and high reliability by arranging a self-diagnosis part monitoring an input/output characteristic of a pressure amplifier arranged inside so as to specify replacement time of the pressure amplifier by detection of performance degradation of the pressure amplifier.

The electropneumatic converter includes a control part generating a targeted input air pressure, a pressure amplifying part generating an output air pressure amplified in accordance with the input air pressure generated by the control part, and a pressure sensor detecting a value of the output air pressure generated by the pressure amplifying part and returning it to the control part. The control part controls the input air pressure based on the value of the output air pressure returned from the pressure sensor. The electropneumatic converter further includes the self-diagnosis part performing a self-diagnosis based on the correlation between a value of the input air pressure output by the control part and a value of the output air pressure detected by the pressure sensor.