A hollow fiber membrane type fluid treatment device having at least a body portion of tubular housing containing a hollow fiber membrane bundle. In the hollow fiber membrane type fluid treatment device, an inner surface of a body portion of the tubular housing at a side of a treatment liquid inlet has a body straight portion and an end tapered portion which increases in diameter toward an end face of the housing body portion, the hollow fiber membrane is arranged so that a distance between the hollow fiber membranes is gradually increased toward the end face on the treatment liquid inlet side along a taper of a tapered portion of the inner surface of the housing body portion, and a liquid to be treated flows within the hollow fiber membranes and a treatment liquid flows outside of the hollow fiber membranes.