An estimation apparatus (2, 2A) for estimating a wear state of tires (T FL, T FR, T RL, T RR) mounted on a vehicle, comprising: a rotation speed acquisition unit configured to sequentially acquire rotation speeds of the tires; a driving force acquisition unit configured to sequentially acquire a driving force of the vehicle; a slip ratio calculation unit configured to calculate a slip ratio based on the sequentially-acquired rotation speeds of the tires; a slope calculation unit configured to calculate a slope of the slip ratio with respect to the driving force based on a large number of data sets of the slip ratio and the driving force, as a regression coefficient indicating a linear relationship between the slip ratio and the driving force; an estimation unit configured to estimate the wear state of the tires based on the slope; and a lateral acceleration acquisition unit configured to sequentially acquire lateral acceleration applied to the vehicle; characterized by further comprising a turn radius acquisition unit configured to acquire a turn radius of the vehicle; and a correction unit configured to correct the slip ratio based on: first relationship information indicating a relationship between the turn radius and the slip ratio, and the turn radius at the time of correction, and/or second relationship information indicating a relationship between the lateral acceleration, the driving force, and the slip ratio, and the lateral acceleration and the driving force at the time of correction. a rotation speed acquisition unit configured to sequentially acquire rotation speeds of the tires; a driving force acquisition unit configured to sequentially acquire a driving force of the vehicle; a slip ratio calculation unit configured to calculate a slip ratio based on the sequentially-acquired rotation speeds of the tires; a slope calculation unit configured to calculate a slope of the slip ratio with respect to the driving force based on a large number of data sets of the slip ratio and the driving force, as a regression coefficient indicating a linear relationship between the slip ratio and the driving force; an estimation unit configured to estimate the wear state of the tires based on the slope; and a lateral acceleration acquisition unit configured to sequentially acquire lateral acceleration applied to the vehicle; characterized by further comprising a turn radius acquisition unit configured to acquire a turn radius of the vehicle; and a correction unit configured to correct the slip ratio based on: first relationship information indicating a relationship between the turn radius and the slip ratio, and the turn radius at the time of correction, and/or second relationship information indicating a relationship between the lateral acceleration, the driving force, and the slip ratio, and the lateral acceleration and the driving force at the time of correction. first relationship information indicating a relationship between the turn radius and the slip ratio, and the turn radius at the time of correction, and/or second relationship information indicating a relationship between the lateral acceleration, the driving force, and the slip ratio, and the lateral acceleration and the driving force at the time of correction.