Abstract: An adjustable flow pump, particularly an air pump, utilizing reciprocal movement of a diaphragm movement bar to achieve pumping. The stroke of the reciprocating diaphragm movement bar can be adjusted without stopping operation of the pump. The diaphragm movement bar is mounted on a pump main body and a swing member is operably coupled to a rotary output shaft of a motor. The rotary output shaft is connected to a cam which imparts motion to the swing member. The movement of the swing member is transmitted, by a linking member, to the reciprocating diaphragm movement bar which then moves along a linear guide. The stroke of the diaphragm movement bar is adjusted by a linear motion mechanism which is operable to change the position of the swing member relative to the diaphragm movement bar.