A high-voltage apparatus includes a battery device, a high-voltage control device, a housing, and a cooling structure. The cooling structure includes a first cooling channel to cool the battery device, a second cooling channel to cool the high-voltage control device, a connection channel connecting the first cooling channel to the second cooling channel, and a ventilator. The connection channel has a first opening portion connected to the first cooling channel, a second opening portion connected to the second cooling channel, and an inner flow path to communicate the first opening portion to the second opening portion. A sectional area of the first opening portion and a sectional area of the second opening portion are each set to be smaller than a sectional area of the inner flow path.