A fluid mixing device provides a gentle rotating and concurrent back and forth motion to agitate a fluid. The device has a receptacle with a shaft extending downwardly from a location off center of its bottom to a link arm which is pivotally attached to a reciprocating drive means. A second embodiment of the invention adds a back and forth rotation of the receptacle about its center by attaching a gear to the bottom of the receptacle about its center and providing a partial inside ring gear along which the gear on the receptacle moves pursuant to the reciprocating movement of the shaft. The device is particularly useful for the mixing of biological solutions from lyophilized materials without creating undesirable foams.