A cylinder characteristic variation sensing device applied to a multi-cylinder internal combustion engine having a plurality of cylinders and a plurality of injectors respectively provided to the cylinders, comprising: a small injection controlling means for performing small injections sequentially in the respective cylinders, thereby injecting a small quantity of fuel from each injector regardless of manipulation performed by a driver to operate the internal combustion engine, the small quantity of fuel being smaller than a fuel quantity of injection which is performed based on the manipulation by the driver for producing output torque of the internal combustion engine; a torque increase amount sensing means (S22, 42) for sensing an increase amount of output torque caused in connection with the small injection or a physical quantity relevant to the increase amount for each cylinder; an injection quantity sensing means (S23, 20a, 200a) for sensing a fluctuation of a fuel inlet pressure at an inlet formed in a housing of the injector caused in connection with the small injection for each cylinder and for sensing an actual injection quantity of the small injection for each cylinder based on the fluctuation of the fuel inlet pressure; and a cylinder characteristic variation calculating means for calculating a variation in a cylinder characteristic among the cylinders based on at least one of a variation in the sensing value of the injection quantity sensing means (S23, 20a, 200a) among the cylinders and a variation in the sensing value of the torque increase amount sensing means (S22, 42) among the cylinders, wherein the small injection controlling means equalizes a predetermined injection quantity among all the cylinders and calculates a command injection period of the injector from a fuel pressure sensed with a fuel pressure sensor and the predetermined small injection quantity for each cylinder, and the small injection controlling means performs the small injections in accordance with the command injection period for each cylinder. a small injection controlling means for performing small injections sequentially in the respective cylinders, thereby injecting a small quantity of fuel from each injector regardless of manipulation performed by a driver to operate the internal combustion engine, the small quantity of fuel being smaller than a fuel quantity of injection which is performed based on the manipulation by the driver for producing output torque of the internal combustion engine; a torque increase amount sensing means (S22, 42) for sensing an increase amount of output torque caused in connection with the small injection or a physical quantity relevant to the increase amount for each cylinder; an injection quantity sensing means (S23, 20a, 200a) for sensing a fluctuation of a fuel inlet pressure at an inlet formed in a housing of the injector caused in connection with the small injection for each cylinder and for sensing an actual injection quantity of the small injection for each cylinder based on the fluctuation of the fuel inlet pressure; and a cylinder characteristic variation calculating means for calculating a variation in a cylinder characteristic among the cylinders based on at least one of a variation in the sensing value of the injection quantity sensing means (S23, 20a, 200a) among the cylinders and a variation in the sensing value of the torque increase amount sensing means (S22, 42) among the cylinders, wherein the small injection controlling means equalizes a predetermined injection quantity among all the cylinders and calculates a command injection period of the injector from a fuel pressure sensed with a fuel pressure sensor and the predetermined small injection quantity for each cylinder, and the small injection controlling means performs the small injections in accordance with the command injection period for each cylinder.