A fuel pressure controlling device for an engine is provided including a fuel injection device, an ignition device, a catalyst for removing pollutants from engine exhaust. A controller selects a combustion mode from at least a homogeneous combustion mode fuel is injected the intake stroke and the fuel is ignited before compression top dead center. The fuel injection device injects the fuel based on a target fuel pressure according to the selected combustion mode. The controller detects whether or not a request is present for raising the temperature of the catalyst. In the homogenous combustion mode, when a request is present, the target fuel pressure is set to a first target fuel pressure, and when a request is not present, the target fuel pressure is set to a second target fuel pressure, the second target fuel pressure being lower than the first target fuel pressure.