An apparatus for identifying between summer tyres and winter tyres based on rotational information obtained from tyres attached to a four-wheeled vehicle equipped with a limited slip differential device (7). The apparatus comprises a rotational information detecting means (1) for detecting rotational information for each of the tyres, a memory means for storing rotational information of each of the tyres, an arithmetic processing means for respectively calculating reciprocals of rolling radii based on rotations information of tyres attached to a driving shaft (5) as well as judged value based on rotational information of each of the tyres, and an identification means for identifying whether the tyres attached to the driving shaft are summer tyres or winter tyres from a relationship between reciprocals of turning radii and the judged value.