A fieldbus adapter (2) connected between a fieldbus (3) that handles a digital signal and a field device (1A-1D) that handles an analog signal, the fieldbus adapter (2) comprising a first connection unit (2b) detachably connected to the fieldbus (3), a second connection unit (2a) detachably connected to the field device (1A-1D), and a conversion unit (23) provided between the first connection unit (2b) and the second connection unit (2a), the conversion unit (23) bidirectionally converting the digital signal handled by the fieldbus (3) and the analog signal handled by the field device (1A-1D).
