A powder amount detector detects an amount of powder in a powder container of a cylindrical shape arranged horizontally. The powder amount detector includes a pair of measuring electrodes configured to detect capacitance between the pair of measuring electrodes to detect the amount of powder. The pair of measuring electrodes is disposed around the powder container. One of the pair of measuring electrodes has a flat shape, and the other of the pair of measuring electrodes has an arc shape following a shape of the powder container.