A gas-insulated switchgear forming a bus section unit used in substations. In a double bus scheme where non-segregated 3-phase gas-insulated buses are laid on a horizontal installation area, this invention applies to a bus structure in which sectionalized gas-insulated main buses arranged in line on the same axis are connected by the bus section unit. By the side of the sectionalized gas-insulated main buses are installed bus section circuit breakers for three phases. A shifted bus section leading from one of the sectionalized main buses is disposed above the third gas-insulated main bus which is located farther from the circuit breaker. The shifted bus section is used to connect the sectionalized main buses. This structure improves the seismic resistance of the bus section unit without increasing the installation area of the unit.