Umbrella stand that is movable on the ground

An umbrella stand, comprising:

• a housing having a bottom provided with an opening;
• and
• an operation mechanism mounted on the housing;
• wherein the operation mechanism includes:
• a support frame mounted in the housing and having two receiving slots formed in two opposite ends thereof;
• two mounting plates each pivotally mounted on the support frame and each aligning with a respective one of the receiving slots of the support frame;
• two pivot shafts each mounted in the support frame and each extended through a respective one of the mounting plates so that each of the mounting plates is pivotally attached to the support frame;
• two castors each rotatably mounted on a respective one of the mounting plates;
• two mounting tubes secured on the support frame;
• a driven rod rotatably mounted in the mounting tubes;
• and
• two pressing plates secured on two opposite ends of the driven rod to rotate in concert with the driven rod and each pressing a respective one of the mounting plates;
• and wherein each of the castor is movable in concert with the respective mounting plate between a first position where each of the castors is retracted into the opening of the housing, and a second position where each of the castors is protruded outward from the opening of the housing.