This paper proposes an approach of object category acquisition based on object shaking behavior. By varying the holding position and shaking the objects, the robots are able to acquire object categories which can be generalized to objects with different size and shape. Experimental results are shown where poor control robot with McKibben actuators acquires and recognizes object categories of three types, namely rigid objects, paper materials and PET bottles with water. The proposed approach seems effective for object categorization of domestic robots. The study also indicates the possible role of object shaking behavior in object category acquisition of infants, which has not been discussed so much in the field of developmental psychology so far.