An image recognition device comprising: a database in which pieces of feature data of a plurality of objects are registered while divided into classes corresponding to each object; an identification unit that identifies an unknown object by evaluating which feature data of the class registered in the database is most similar to feature data obtained from an image of the unknown object; and a feature data registration unit that registers feature data in the database, wherein the database configured to set a plurality of classes to an identical object, and the feature data registration unit, in adding new feature data of an object which is identical to a first object already registered in the database, sets a new class other than an existing class of the first object, and registers the new feature data in the new class, when a second object satisfying a predetermined similar condition with the new feature data exists in the database; wherein the predetermined similar condition includes at least one of (i) a condition that a similarity between the new feature data and feature data of a class of the second object is higher than a similarity between the new feature data and feature data of the existing class of the first object and that an intra-class variance of the existing class of the first object increases when the new feature data is added to the existing class; (ii) a condition that a similarity between the new feature data and the feature data of the class of the second object is higher than a threshold and that an intra-class variance of the existing class of the first object increases when the new feature data is added to the existing class; (iii) a condition that an intra-class variance of the existing class of the first object increases and an inter-class variance between the existing class of the first object and the class of the second object decreases when the new feature data is added to the existing class of the first object; and (iv) a condition that distinguishability, by the identification unit, between the first object and the second object is degraded when the new feature data is added to the existing class of the first object. a database in which pieces of feature data of a plurality of objects are registered while divided into classes corresponding to each object; an identification unit that identifies an unknown object by evaluating which feature data of the class registered in the database is most similar to feature data obtained from an image of the unknown object; and a feature data registration unit that registers feature data in the database, wherein the database configured to set a plurality of classes to an identical object, and the feature data registration unit, in adding new feature data of an object which is identical to a first object already registered in the database, sets a new class other than an existing class of the first object, and registers the new feature data in the new class, when a second object satisfying a predetermined similar condition with the new feature data exists in the database; wherein the predetermined similar condition includes at least one of (i) a condition that a similarity between the new feature data and feature data of a class of the second object is higher than a similarity between the new feature data and feature data of the existing class of the first object and that an intra-class variance of the existing class of the first object increases when the new feature data is added to the existing class; (ii) a condition that a similarity between the new feature data and the feature data of the class of the second object is higher than a threshold and that an intra-class variance of the existing class of the first object increases when the new feature data is added to the existing class; (iii) a condition that an intra-class variance of the existing class of the first object increases and an inter-class variance between the existing class of the first object and the class of the second object decreases when the new feature data is added to the existing class of the first object; and (iv) a condition that distinguishability, by the identification unit, between the first object and the second object is degraded when the new feature data is added to the existing class of the first object. (i) a condition that a similarity between the new feature data and feature data of a class of the second object is higher than a similarity between the new feature data and feature data of the existing class of the first object and that an intra-class variance of the existing class of the first object increases when the new feature data is added to the existing class; (ii) a condition that a similarity between the new feature data and the feature data of the class of the second object is higher than a threshold and that an intra-class variance of the existing class of the first object increases when the new feature data is added to the existing class; (iii) a condition that an intra-class variance of the existing class of the first object increases and an inter-class variance between the existing class of the first object and the class of the second object decreases when the new feature data is added to the existing class of the first object; and (iv) a condition that distinguishability, by the identification unit, between the first object and the second object is degraded when the new feature data is added to the existing class of the first object.