A fuel pump controller adapted for an internal combustion engine, wherein the internal combustion engine includes a first high-pressure fuel pump configured to discharge fuel by increasing pressure, a first fuel passage (37, 41), through which the fuel discharged by the first high-pressure fuel pump flows, a first fuel injection valve configured to inject the fuel supplied from the first fuel passage (37, 41), a second high-pressure fuel pump configured to discharge fuel by increasing pressure, a second fuel passage (57, 61), through which the fuel discharged by the second high-pressure fuel pump flows, a second fuel injection valve configured to inject the fuel supplied from the second fuel passage (57, 61), and a connecting passage, which connects the first fuel passage (37, 41) and the second fuel passage (57, 61) to each other, such that the fuel inside the first fuel pipe (37, 41), and the fuel inside the second fuel pipe (57, 61) can flow into each other via the connecting passage so that the actual fuel pressure inside the first fuel pipe (37, 41), the second fuel pipe (57, 61), and the connecting passage is almost the same, characterized in that the internal combustion engine further includes: a temperature sensor configured to detect an ambient temperature of the first high-pressure fuel pump or the second high-pressure fuel pump, wherein the fuel pump controller comprises a pump switching unit configured to switch a drive mode of the first high-pressure fuel pump and the second high-pressure fuel pump, in accordance with an operating state of the internal combustion engine, either to a twin-drive mode, in which both the first high-pressure fuel pump and the second high-pressure fuel pump are driven, or to a single-drive mode, in which either one of the first high-pressure fuel pump and the second high-pressure fuel pump is driven, and the pump switching unit is configured to switch to the twin-drive mode in a state that the single-drive mode is performed in a case where the ambient temperature detected by the temperature sensor becomes equal to or higher than a first temperature at which the fuel inside one of the first high-pressure fuel pump and the second high-pressure fuel pump that has been stopped boils to generate vapor. a first high-pressure fuel pump configured to discharge fuel by increasing pressure, a first fuel passage (37, 41), through which the fuel discharged by the first high-pressure fuel pump flows, a first fuel injection valve configured to inject the fuel supplied from the first fuel passage (37, 41), a second high-pressure fuel pump configured to discharge fuel by increasing pressure, a second fuel passage (57, 61), through which the fuel discharged by the second high-pressure fuel pump flows, a second fuel injection valve configured to inject the fuel supplied from the second fuel passage (57, 61), and a connecting passage, which connects the first fuel passage (37, 41) and the second fuel passage (57, 61) to each other, such that the fuel inside the first fuel pipe (37, 41), and the fuel inside the second fuel pipe (57, 61) can flow into each other via the connecting passage so that the actual fuel pressure inside the first fuel pipe (37, 41), the second fuel pipe (57, 61), and the connecting passage is almost the same,