A gas insulated switching apparatus comprising a power transmission and reception line unit connected to a bus-bar (3, 4) extending in a horizontal direction and a transformer line unit disposed adjacent to the power transmission and reception line unit and connected to the bus-bar (3, 4), wherein the power transmission and reception line unit includes a first breaker disposed such that an axis thereof is perpendicular to an installation surface, a first bus-bar side disconnector (13, 14) that is connected to a side surface of the first breaker and is connected to the bus-bar (3, 4), a connection tank (25, 26) having a first connection port opening to a first breaker side and connected, via the first connection port, to the side surface of the first breaker on an opposite side of a bus-bar side, a first line side disconnector connected to the connection tank (25, 26) via a second connection port of the connection tank (25, 26) opening in an opposite direction to the first connection port, a first cable head that is connected to a bottom of the first line side disconnector and is connected to a first power cable, a second line side disconnector that is connected to the connection tank (25, 26) via a third connection port of the connection tank (25, 26) opening in a same direction as the second connection port, the third connection port being disposed at an interval between units in an extension direction in which the bus-bar (3,4) extends with respect to the second connection port, and a second cable head that is connected to a bottom of the second line side disconnector and is connected to a second power cable, the transformer line unit includes a second breaker disposed such that an axis thereof is perpendicular to the installation surface, a second bus-bar side disconnector (6, 7) that is connected to a side surface of the second breaker and is connected to the bus-bar (3, 4), a third line side disconnector connected to the side surface of the second breaker on an opposite side of the bus-bar side, and a third cable head that is connected to a bottom of the third line side disconnector and is connected to a third power cable, when viewed from the first breaker, the first cable head is disposed in a unit direction that is a horizontal direction orthogonal to the extension direction in which the bus-bar (3, 4) extends, the first and second cable heads (18, 20) are arranged in the extension direction in which the bus-bar (3, 4) extends at an interval between the units, when viewed from the second breaker, the second cable head is disposed behind the third cable head in the unit direction, and a part of the connection tank (25, 26) including the third connection port is disposed between the third cable head and the second cable head in the unit direction. a first breaker disposed such that an axis thereof is perpendicular to an installation surface, a first bus-bar side disconnector (13, 14) that is connected to a side surface of the first breaker and is connected to the bus-bar (3, 4), a connection tank (25, 26) having a first connection port opening to a first breaker side and connected, via the first connection port, to the side surface of the first breaker on an opposite side of a bus-bar side, a first line side disconnector connected to the connection tank (25, 26) via a second connection port of the connection tank (25, 26) opening in an opposite direction to the first connection port, a first cable head that is connected to a bottom of the first line side disconnector and is connected to a first power cable, a second line side disconnector that is connected to the connection tank (25, 26) via a third connection port of the connection tank (25, 26) opening in a same direction as the second connection port, the third connection port being disposed at an interval between units in an extension direction in which the bus-bar (3,4) extends with respect to the second connection port, and a second cable head that is connected to a bottom of the second line side disconnector and is connected to a second power cable, a second breaker disposed such that an axis thereof is perpendicular to the installation surface, a second bus-bar side disconnector (6, 7) that is connected to a side surface of the second breaker and is connected to the bus-bar (3, 4), a third line side disconnector connected to the side surface of the second breaker on an opposite side of the bus-bar side, and a third cable head that is connected to a bottom of the third line side disconnector and is connected to a third power cable,