A foot support device applicable to a surgery table for locating and supporting a patient's foot, which includes: a main body; a space being formed in the main body; a bottom end of the main body being connectable to the surgery table; an operation member up and down movably fitted around the main body, the operation member having an insertion pin therein; and a support including a bracket and at least one support body; an insertion hole is formed on the bracket. The bracket is rotatably mounted in the space of the main body. When the operation member is moved downward, the insertion pin is inserted into the insertion hole of the bracket to fix the support. By means of rotating the operation member, the operation member can be latched with the main body.