A switch failure detection device comprising: a plurality of switches (Q1, Q2, Q31 to Q36) respectively provided on a plurality of branch paths (L1, L2, L31 to L36), a current path branching into the plurality of branch paths; a plurality of current detection units (14, 140) provided on the plurality of branch paths respectively, each of the current detection units being configured to detect an electrical current (I1, I2, I31 to I36) flowing through each of the plurality of branch paths; a first switch control unit (15, 150) configured to turn off at least one of the plurality of switches and turn on the other ones of the plurality of switches, the first switch control unit being configured to switch the at least one of the plurality of switches to be turned off one by one to another one of the plurality of switches; and a failure detection unit (15, 150) configured to detect a failure of the switches based on a comparison between a predetermined value and a value of the current detected by each of the plurality of current detection units while the switches are being turned on or off by the first switch control unit; wherein each of the current detection units is configured to output a current detection signal in accordance with the electrical current flowing through each of the plurality of branch paths; characterized in that the switch failure detection device further comprises: a storage unit configured to store an initial value of the current detection signal, the initial value being to be output from each of the current detection units when the plurality of switches are turned off, wherein the failure detection unit is a first failure detection unit configured to compare the initial value and a value of a first current detection signal output from corresponding one of the current detection units when the one of the plurality of switches is turned off by the first switch control unit, the first failure detection unit being configured to detect a first failure of the plurality of switches based on a result of the comparison. a plurality of switches (Q1, Q2, Q31 to Q36) respectively provided on a plurality of branch paths (L1, L2, L31 to L36), a current path branching into the plurality of branch paths; a plurality of current detection units (14, 140) provided on the plurality of branch paths respectively, each of the current detection units being configured to detect an electrical current (I1, I2, I31 to I36) flowing through each of the plurality of branch paths; a first switch control unit (15, 150) configured to turn off at least one of the plurality of switches and turn on the other ones of the plurality of switches, the first switch control unit being configured to switch the at least one of the plurality of switches to be turned off one by one to another one of the plurality of switches; and a failure detection unit (15, 150) configured to detect a failure of the switches based on a comparison between a predetermined value and a value of the current detected by each of the plurality of current detection units while the switches are being turned on or off by the first switch control unit; wherein each of the current detection units is configured to output a current detection signal in accordance with the electrical current flowing through each of the plurality of branch paths; characterized in that a storage unit configured to store an initial value of the current detection signal, the initial value being to be output from each of the current detection units when the plurality of switches are turned off, wherein the failure detection unit is a first failure detection unit configured to compare the initial value and a value of a first current detection signal output from corresponding one of the current detection units when the one of the plurality of switches is turned off by the first switch control unit, the first failure detection unit being configured to detect a first failure of the plurality of switches based on a result of the comparison.