Abstract: In an information processing apparatus, an internal variable holding unit holds a smaller number of values of an internal variable than N, the internal variable being sequentially calculated in time series based on sensor data acquired by a sensor data acquisition unit. An internal variable calculation unit calculates the internal variable corresponding to a (j+1)-th time point (j is an integer of one to N?1) based on the sensor data at the (j+1)-th time point and the internal variable corresponding to a j-th time point. A feature calculation unit calculates a feature by extracting a statistical characteristic included in the sensor data from the first time point to the N-th time point based on the internal variable at the N-th time point. A state diagnosis unit makes a diagnosis of a state of the mechanical apparatus based on the feature.