The invention discloses an inner oblique gear grinding machine comprising a lathe bed. A small vertical column with the fixed position and a large vertical column driven to move in the X-axis direction by an X-direction driving mechanism are arranged on the lathe bed, a work table mechanism for machining oblique gears is arranged between the large vertical column and the small vertical column, and a first Z-direction sliding rail is fixedly connected to one side of the large vertical column. A head grinding mechanism is slidably connected to the first Z-direction sliding rail through a first Z-direction sliding plate, a second Z-direction sliding rail is fixedly connected to the side, opposite to the head grinding mechanism, of the small vertical column, and a roller dressing mechanism is slidably connected to the second Z-direction sliding rail through a second Z-direction sliding plate. According to the inner oblique gear grinding machine, grinding wheel dressing is convenient, the automation degree is increased, the rigidity and accuracy are improved, and the cost is reduced.