A control device for an engine in which partial compression-ignition combustion is executed at least within a part of an operating range of the engine, the partial compression-ignition combustion including spark ignition combustion and compression ignition combustion, the spark ignition being to be performed by combusting a portion of a mixture gas inside a cylinder by spark-ignition and followed by the compression ignition combustion, the compression ignition being to be performed by causing the remaining mixture gas inside the cylinder to self-ignite, the control device comprising: an in-cylinder pressure sensor configured to detect at least pressure inside the cylinder; a manipulator (13a, 14a, 53) configured to change an EGR ratio that is a ratio of exhaust gas recirculated into the cylinder; and a controller configured to control the manipulator (13a, 14a, 53) to increase the EGR ratio based on the detected pressure of the in-cylinder pressure sensor, wherein the controller is configured to control the manipulator (13a, 14a, 53) to increase the EGR ratio when a noise index value specified based on the detected pressure of the in-cylinder pressure sensor is confirmed to exceed a given threshold during the partial compression-ignition combustion, the controller is configured to select one of a first mode and a second mode, as a combustion mode of the partial compression-ignition combustion, in the first mode the partial compression-ignition combustion is performed in an environment in which an air-fuel ratio, which is a ratio of air to fuel inside the cylinder, becomes higher than a stoichiometric air-fuel ratio, in the second mode the partial compression-ignition combustion is performed in an environment in which a gas/fuel ratio, which is a ratio of entire gas in the cylinder to the fuel inside the cylinder, is higher than the stoichiometric air-fuel ratio and the air-fuel ratio is substantially the stoichiometric air-fuel ratio, the controller is configured to switch the combustion mode from the first mode to the second mode, when the noise index value is confirmed to exceed the given threshold during the partial compression-ignition combustion in the first mode, the controller is configured to select one of the first mode and the second mode, as the combustion mode, when the engine operates in a specific condition (A1, A2), and the specific condition corresponds to that the engine is in a warmed-up state and an operation point (P1, P2) of the engine is within a given low engine load range. an in-cylinder pressure sensor configured to detect at least pressure inside the cylinder; a manipulator (13a, 14a, 53) configured to change an EGR ratio that is a ratio of exhaust gas recirculated into the cylinder; and a controller configured to control the manipulator (13a, 14a, 53) to increase the EGR ratio based on the detected pressure of the in-cylinder pressure sensor, wherein the controller is configured to control the manipulator (13a, 14a, 53) to increase the EGR ratio when a noise index value specified based on the detected pressure of the in-cylinder pressure sensor is confirmed to exceed a given threshold during the partial compression-ignition combustion, the controller is configured to select one of a first mode and a second mode, as a combustion mode of the partial compression-ignition combustion, in the first mode the partial compression-ignition combustion is performed in an environment in which an air-fuel ratio, which is a ratio of air to fuel inside the cylinder, becomes higher than a stoichiometric air-fuel ratio, in the second mode the partial compression-ignition combustion is performed in an environment in which a gas/fuel ratio, which is a ratio of entire gas in the cylinder to the fuel inside the cylinder, is higher than the stoichiometric air-fuel ratio and the air-fuel ratio is substantially the stoichiometric air-fuel ratio, the controller is configured to switch the combustion mode from the first mode to the second mode, when the noise index value is confirmed to exceed the given threshold during the partial compression-ignition combustion in the first mode, the controller is configured to select one of the first mode and the second mode, as the combustion mode, when the engine operates in a specific condition (A1, A2), and the specific condition corresponds to that the engine is in a warmed-up state and an operation point (P1, P2) of the engine is within a given low engine load range.