Apparatus and method for determining a state of a hybrid power train

An apparatus and method determine a state of a power train that includes a power transmission apparatus that is configured to transmit power of a first driving power source to an input side of a second driving power source via a clutch and a transmission, and is capable of changing a torque capacity of the clutch and a gear ratio of the transmission. The apparatus and method determine a state of the clutch or the transmission based on a revolution speed of the first driving power source and information indicating a state of the second driving power source, e.g., a revolution speed of the input side of the second driving power source.