Microgravity experiments were performed to evaluate liquid propellant retention force of a porous metal. In our gas-liquid equilibrium propulsion system, porous metals are equipped in a storage tank and surface tension in pores of the porous metals holds liquid propellant in them, which ensures expelling of only gaseous propellant from a storage tank. The performance of a porous metal for liquid retention was evaluated by two different microgravity experiments. In the first one, the acrylic tank filled with semilunar porous metals and liquid propellant was rotated by a motor. The performance was evaluated by considering a force balance between liquid retention force and centrifugal force acting on the liquid propellant absorbed in porous metals. In the other one, the internal pressure in the tank was reduced by propellant ejection from a nozzle. The performance was evaluated by exhaustion time. As a result, it was found that liquid retention force was equal to, or higher than analytical value (bubble point pressure), and extractable gas volume of each ejection strongly depends on the existence of bubbles in liquid propellant.