An apparatus for identifying the state of a signal light includes a processor configured to input time series images into a first classifier to detect object regions each including a vehicle equipped with a signal light in the respective images, the first classifier having been trained to detect the vehicle; chronologically input characteristics obtained from pixel values of the object regions detected in the respective images into a second classifier to calculate confidence scores of possible candidate states of the signal light of the vehicle, the second classifier having a recursive structure or performing a convolution operation in a temporal direction; and identify the state of the signal light, based on the preceding state of the signal light, information indicating whether transitions between the candidate states of the signal light are allowed, and the confidence scores of the respective candidate states.