Attachable power device for bike

An attachable power device for a bike characterized as being installed in a bike in which a front wheel and a rear wheel are installed in the front and rear sides of a reverse triangle frame, and a front sprocket connected with pedals is installed in an intermediate lower portion of the same, and a multi-stage gear sprocket is installed in a right side of a hub of the rear wheel, and a chain connects the front sprocket and the multi-stage gear sprocket, comprising:

• a base plate installed in an upper side of the rear wheel;
• a motor and a decelerator which are installed in one side of an upper side of the base plate;
• an inner casing which includes a power supply unit for supplying power to the motor and is detachably attached to the other side of an upper side of the base plate;
• an outer casing which is configured to accommodate the inner casing, the motor and the decelerator and is engaged to an upper side of the base plate;
• a chain sprocket which is installed in a left side of the hub of the rear wheel;
• a connection member which connects the chain sprocket and the driving sprocket of the decelerator;
• and
• a control unit which is installed in the handle and controls a driving of the motor.