An isolating and grounding switch mechanism (1) and a gas-insulated metal-enclosed switchgear. The isolating and grounding switch mechanism (1) comprises a housing (19), an isolating switch (12), and a grounding switch (11). The isolating switch (12) comprises an isolating switch moving contact (124) and an isolating switch stationary contact (123) that are provided in parallel along an axial direction. The grounding switch (11) comprises a grounding switch moving contact (112) and a grounding switch stationary contact (113). The interior of the housing (19) is provided with a transformer connection terminal (145), an external connection terminal for connection to a main loop access conductive structure, and a guide contact base (14) and a connection contact base (15) horizontally provided in parallel along the axial direction. The transformer connection terminal (145) is provided on the guide contact base (14). The isolating switch stationary contact (123) is provided at a position of the connection contact base (15) facing the guide contact base (14). The external connection terminal is provided at a position of the connection contact base (15) that allows access of the main loop access conductive structure along the axial direction. The isolating switch moving contact (124) is axially guided to pass through the guide contact base (14), and has a switching-on station that is in contact fit with the connection contact base (15).