A working machine (1; 200) comprising: a communication adapter attachment device (8; 208), wherein the communication adapter attachment device (8; 208) comprises an adapter housing portion (10; 210) provided inside the working machine (1; 200), and having an opening on an outer surface of the working machine (1; 200), the adapter housing portion (10; 210) configured to accommodate a communication adapter that is detachable through the opening, wherein the adapter housing portion (10; 210) includes a connector coupled to a controller of the working machine (1; 200), and wherein the communication adapter is configured to be attached to the connector and is electrically coupled to the controller via the connector when attached, wherein the communication adapter includes an adapter case accommodating a module substrate, wherein two or more strip-shaped insertion pieces (71, 72, 73, 74) are provided at a first end of the module substrate, wherein each of the two or more insertion pieces includes a first surface and a second surface, the first surface includes a first contact (81, 82, 83, 84) and the second surface includes a second contact (85, 86, 87, 88), wherein the connector includes a connector housing comprising an adapter insertion opening through which the communication adapter is inserted from the adapter insertion opening side to an adapter insertion space of the connector housing, wherein the connector housing comprises two or more insertion slots (46a, 46b, 46c, 46d), wherein each of the insertion pieces (71, 72, 73, 74) is inserted into a corresponding one of the insertion slots (46a, 46b, 46c, 46d), wherein each of the insertion slots (46a, 46b, 46c, 46d) comprises a first terminal (91, 92) and a second terminal (93, 94), the first terminal being configured to be brought in contact and electrically conductive with the first contact and the second terminal being configured to be brought in contact and electrically conductive with the second contact. a communication adapter attachment device (8; 208), wherein the communication adapter attachment device (8; 208) comprises an adapter housing portion (10; 210) provided inside the working machine (1; 200), and having an opening on an outer surface of the working machine (1; 200), the adapter housing portion (10; 210) configured to accommodate a communication adapter that is detachable through the opening, wherein the adapter housing portion (10; 210) includes a connector coupled to a controller of the working machine (1; 200), and wherein the communication adapter is configured to be attached to the connector and is electrically coupled to the controller via the connector when attached, wherein the communication adapter includes an adapter case accommodating a module substrate, wherein two or more strip-shaped insertion pieces (71, 72, 73, 74) are provided at a first end of the module substrate, wherein each of the two or more insertion pieces includes a first surface and a second surface, the first surface includes a first contact (81, 82, 83, 84) and the second surface includes a second contact (85, 86, 87, 88), wherein the connector includes a connector housing comprising an adapter insertion opening through which the communication adapter is inserted from the adapter insertion opening side to an adapter insertion space of the connector housing, wherein the connector housing comprises two or more insertion slots (46a, 46b, 46c, 46d), wherein each of the insertion pieces (71, 72, 73, 74) is inserted into a corresponding one of the insertion slots (46a, 46b, 46c, 46d), wherein each of the insertion slots (46a, 46b, 46c, 46d) comprises a first terminal (91, 92) and a second terminal (93, 94), the first terminal being configured to be brought in contact and electrically conductive with the first contact and the second terminal being configured to be brought in contact and electrically conductive with the second contact.