An abnormality detection device includes: a receiver, a reception predictor, frame information storage, and an abnormality determiner. The receiver receives a communication frame via a communication network. The frame information storage stores information regarding the communication frame. The reception predictor calculates and sets a predicted time range including a scheduled reception time of the communication frame of a target frame type from among a plurality of frame types received by the receiver by referencing the frame information storage and the reception time of the communication frame when the communication frame is received. The abnormality determiner determines the target communication frame is an abnormal frame when the target communication frame is received at a time outside the predicted reception range.