A developing device (3a, 3b, 3c, 3d) comprising: a developing roller disposed opposite to an image carrying member (1a, 1b, 1c, 1d) on which an electrostatic latent image is formed, the developing roller being configured to feed toner to the image carrying member (1a, 1b, 1c, 1d) in an opposing region where the developing roller and the image carrying member (1a, 1b, 1c, 1d) face each other; a toner feeding roller disposed opposite to the developing roller, the toner feeding roller being configured to feed toner to the developing roller in an opposing region where the toner feeding roller and the developing roller face each other; a thickness regulating member disposed opposite to the toner feeding roller at a predetermined distance from the toner feeding roller, the thickness regulating member being configured to regulate a thickness of toner carried on the toner feeding roller; and a casing that holds therein the developing roller, the toner feeding roller, and the thickness regulating member, wherein the thickness regulating member is disposed below the opposing region where the developing roller and the toner feeding roller face each other, the thickness regulating member is formed in a roller shape, and the thickness regulating member is rotatable in a same direction as a direction in which the toner feeding roller rotates during a developing operationm and characterised in that the thickness regulating member is configured to rotate while the developing operation is not performed, and the toner feeding roller is configured to rotate in a direction opposite to a direction in which the thickness regulating member rotates when the thickness regulating member rotates. a developing roller disposed opposite to an image carrying member (1a, 1b, 1c, 1d) on which an electrostatic latent image is formed, the developing roller being configured to feed toner to the image carrying member (1a, 1b, 1c, 1d) in an opposing region where the developing roller and the image carrying member (1a, 1b, 1c, 1d) face each other; a toner feeding roller disposed opposite to the developing roller, the toner feeding roller being configured to feed toner to the developing roller in an opposing region where the toner feeding roller and the developing roller face each other; a thickness regulating member disposed opposite to the toner feeding roller at a predetermined distance from the toner feeding roller, the thickness regulating member being configured to regulate a thickness of toner carried on the toner feeding roller; and a casing that holds therein the developing roller, the toner feeding roller, and the thickness regulating member, wherein the thickness regulating member is disposed below the opposing region where the developing roller and the toner feeding roller face each other, the thickness regulating member is formed in a roller shape, and the thickness regulating member is rotatable in a same direction as a direction in which the toner feeding roller rotates during a developing operationm and characterised in that the thickness regulating member is configured to rotate while the developing operation is not performed, and the toner feeding roller is configured to rotate in a direction opposite to a direction in which the thickness regulating member rotates when the thickness regulating member rotates.