A switch module comprising: a master switch unit comprising: a master substrate; a determination unit mounted on the master substrate and configured to determine an ON/OFF state of a switch portion (21, 22) connected to the determination unit; a master-side switch portion mounted on the master substrate and connected to the determination unit; and at least one master-side connector mounted on the master substrate and connected to the determination unit; and at least one slave switch unit comprising: a slave substrate; a slave-side switch portion mounted on the slave substrate; and a first slave-side connector mounted on the slave substrate and connected to the slave-side switch portion, wherein the master switch unit includes a plurality of the master-side connectors, the slave switch unit includes a pair of the first slave-side connector, and a pair of second slave-side connectors mounted on the slave substrate and connected to each other, a plurality of the slave switch units are provided, one of the plurality of master-side connectors is connected to one of the pair of first slave-side connectors in one of the first slave switch units, another of the plurality of master-side connectors is connected to one of the pair of second slave-side connectors in the one of the first slave switch units, the other of the pair of second slave-side connectors in the one of the first slave switch units is connected to one of the pair of first slave-side connector of a second slave switch unit among the plurality of slave switch units, and the other of the pair of first slave-side connectors in the one of the first slave switch units is connected to one of the pair of the second slave-side connector of the second slave switch unit among the plurality of slave switch units. a master switch unit comprising: a master substrate; a determination unit mounted on the master substrate and configured to determine an ON/OFF state of a switch portion (21, 22) connected to the determination unit; a master-side switch portion mounted on the master substrate and connected to the determination unit; and at least one master-side connector mounted on the master substrate and connected to the determination unit; and a master substrate; a determination unit mounted on the master substrate and configured to determine an ON/OFF state of a switch portion (21, 22) connected to the determination unit; a master-side switch portion mounted on the master substrate and connected to the determination unit; and at least one master-side connector mounted on the master substrate and connected to the determination unit; and at least one slave switch unit comprising: a slave substrate; a slave-side switch portion mounted on the slave substrate; and a first slave-side connector mounted on the slave substrate and connected to the slave-side switch portion, wherein a slave substrate; a slave-side switch portion mounted on the slave substrate; and a first slave-side connector mounted on the slave substrate and connected to the slave-side switch portion, wherein the master switch unit includes a plurality of the master-side connectors, the slave switch unit includes a pair of the first slave-side connector, and a pair of second slave-side connectors mounted on the slave substrate and connected to each other, a plurality of the slave switch units are provided, one of the plurality of master-side connectors is connected to one of the pair of first slave-side connectors in one of the first slave switch units, another of the plurality of master-side connectors is connected to one of the pair of second slave-side connectors in the one of the first slave switch units, the other of the pair of second slave-side connectors in the one of the first slave switch units is connected to one of the pair of first slave-side connector of a second slave switch unit among the plurality of slave switch units, and the other of the pair of first slave-side connectors in the one of the first slave switch units is connected to one of the pair of the second slave-side connector of the second slave switch unit among the plurality of slave switch units.