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 a fuel injection time ta is very longer than a pulsation time t2 (YES in step S14), an ECU sets a current time to the switching timing (step S15). Further, when an injection interval tc is longer than the pulsation time t2 (YES in step S16), the switching timing is set so that the pulsation time t2 starts simultaneously with the completion of the fuel injection (step S17). When the pulsation time t2 is longer than the time obtained by adding the fuel injection time ta to the fuel injection interval tc before and after the fuel injection time ta (YES in step S18), the switching timing is set in accordance with a node part time t3 (step S19).