A fuel injection control device includes a reference interval calculation section that calculates a reference interval between an end time of a decrease interval where the pressure decreases as a fuel injection rate increases and a start time of an increase interval where the pressure increases as the fuel injection rate decreases on a pressure waveform detected by the pressure sensor, an integration interval setting section that sets, in the reference interval, an integration interval where an influence of a disturbance on the fuel pressure decrease due to a target injection is suppressible, and a decrease amount calculation section that calculates a corresponding pressure decrease amount, which is a fuel pressure decrease amount corresponding to a maximum injection rate of fuel of the target injection, based on an integral value obtained by integrating the fuel pressure decrease amount due to the target injection in the integration interval.