A facility diagnosis device includes: a process data acquirer that acquires process data indicating a state of a process executed in a plant; a production data acquirer that acquires production data indicating a production state in the plant; a state information generator that generates state information for estimating an operation state of a facility operating in the process based on the acquired process data or the acquired production data, or the process data and the production data; and a determiner that determines the operation state of the facility based on the acquired process data or the generated state information and the acquired production data.