To provide a fuel supply device capable of improving fuel economy, by optimizing the timing for instructing fuel pressure switching, and by preventing the actual fuel injection amount from being deviated from a desired fuel injection amount even when the fuel pressure is switched.

When an injection interval tc is larger than a variation time t2 of a fuel pressure (YES in step S14), an ECU controls a switching valve so that the variation time t2 starts simultaneously with the completion of the fuel injection in the next cylinder in which the fuel injection is performed. Further, when the variation time t2 is shorter than the time obtained by adding a predetermined time α to the injection interval tc (YES in step S15), the ECU controls so that the variation time t2 starts simultaneously with the completion of the fuel injection in the next cylinder in which the fuel injection is performed. In contrast, when the variation time t2 is equal to or more than the time obtained by adding the predetermined time α to the injection interval tc, the ECU avoids the setting of the switching timing of the fuel pressure (YES in step S17).