Step stool

A step tool, includes front leg tubes, rear leg tubes, bottom footplate, top footplate, a connecting device for connecting the footplates and the leg tubes, lock catch device of the top footplate, the front leg tubes joint to the rear leg tubes rotatably, the foreside of the top footplate joints to the front leg tubes rotatably, a rail is fixed on the rear leg tubes, the lock catch device disposed on the top footplate is detachedly connecting to the rail, wherein:

• The lock catch device includes:
• Two connecting ears, which are disposed on the top footplate with space between in the right and left and stick out of the bottom side of the top footplate;
• A rotation axis, which passes through the two connecting ears rotatably;
• A lock catch fixed to the rotation axis is disposed with hook rabbet to hook the rail from the outsides towards the inner;
• and
• A torsion spring, which interlinks the rotation axis and generates torque to rotate the rotation axis, the both ends of the torsion spring support against the footplate and the lock catch separately.