1. A control device for a multi-cylinder internal combustion engine that includes fuel injection valves that respectively directly inject fuel into corresponding cylinders, a rotation angle sensor that detects a rotation angle of an engine output shaft and a fuel pressure sensor that detects a fuel pressure inside each fuel injection valve or in a system that supplies fuel to each fuel injection valve, the control device comprising: a controller configured to: (i) execute a first learning process in a predetermined engine operating state, the first learning process updating a correction value for individually correcting a control value for each fuel injection valve as a first learned value, based on a rotation fluctuation of the engine output shaft in each cylinder detected by the rotation angle sensor, and the first learning process reducing a degree of deviation in the rotation fluctuation among the cylinders, (ii) execute a second learning process in the predetermined engine operating state, the second process updating a correction value for individually correcting a control value for each fuel injection valve as a second learned value, based on the fuel pressure detected by the fuel pressure sensor, and (iii) decrease a learning rate of the second learned value in the predetermined engine operating state until the first learned value converges for the first time as compared with the learning rate of the second learned value after the first learned value has converged.