A paper feeding device comprising: a paper feeding cassette that holds a plurality of sheets and has a stacking surface with an angle A relative to horizontal that changes depending on a quantity of sheets stacked thereon; a pickup roller that feeds the plurality of sheets from the paper feeding cassette; at least one separation roller arranged downstream from the paper feeding cassette in a transport direction of the plurality of sheets and configured to separate the plurality of sheets from each other in a case where the plurality of sheets are fed from the paper feeding cassette in an overlapped state; a guide unit arranged between the paper feeding cassette and the at least one separation roller, the guide unit having a guide surface which is inclined upwards on a downstream side thereof in the transport direction of the plurality of sheets; a drive unit configured to change an angle B of the guide surface relative to horizontal; and a control unit configured to control the drive unit to change the angle B based on the angle A; characterized in that the paper feeding device further comprises a stacking surface angle detecting sensor that detects the angle A and outputs the detected angle A to the control unit; wherein the control unit is configured to control the drive unit such that angle B is a first inclination angle when angle A is smaller than a predetermined angle threshold, and angle B is a second inclination angle which is larger than the first inclination angle when angle A is larger than the predetermined angle threshold, based on the output from the stacking surface angle detecting sensor. a paper feeding cassette that holds a plurality of sheets and has a stacking surface with an angle A relative to horizontal that changes depending on a quantity of sheets stacked thereon; a pickup roller that feeds the plurality of sheets from the paper feeding cassette; at least one separation roller arranged downstream from the paper feeding cassette in a transport direction of the plurality of sheets and configured to separate the plurality of sheets from each other in a case where the plurality of sheets are fed from the paper feeding cassette in an overlapped state; a guide unit arranged between the paper feeding cassette and the at least one separation roller, the guide unit having a guide surface which is inclined upwards on a downstream side thereof in the transport direction of the plurality of sheets; a drive unit configured to change an angle B of the guide surface relative to horizontal; and a control unit configured to control the drive unit to change the angle B based on the angle A; characterized in that the paper feeding device further comprises a stacking surface angle detecting sensor that detects the angle A and outputs the detected angle A to the control unit; wherein the control unit is configured to control the drive unit such that angle B is a first inclination angle when angle A is smaller than a predetermined angle threshold, and angle B is a second inclination angle which is larger than the first inclination angle when angle A is larger than the predetermined angle threshold, based on the output from the stacking surface angle detecting sensor.