To provide a dry dehumidifier which is reduced in energy consumption and can reduce costs and keep a dew point constant in a room.

In the dry dehumidifier, a rotor partitioned into a dehumidification part and a regeneration part is provided, treatment air is dehumidified by being passed through the dehumidification part while being rotated, dry air of a low dew point is supplied to an aimed chamber, and heated air is passed through the regeneration part to regenerate the rotor. A bypass communicating with the front and rear of the bypass is formed, the flow rate of air passing through the bypass is controlled, treatment air of a high dew point before passing through the dehumidification part is mixed with the dry air of a low dew point after passing through the dehumidification part, and the dew point temperature of the dry air to be supplied is controlled in a short time.