Provided is a method for the selective differentiation into M1 macrophages under a pressurized environment, and more particularly, a method for the selective differentiation of undifferentiated macrophages into M1 macrophages, the method including incubating the undifferentiated macrophages in an incubator under the pressurized environment. In addition, provided is a method for producing osteoclasts, the method including: incubating undifferentiated macrophages in an incubator under a pressurized environment to differentiate into M1 macrophages; and differentiating the differentiated M1 macrophages into osteoclasts.