PROBLEM TO BE SOLVED: To provide a guide device that introduces a guide wire in a pericardial space even if a puncture needle tears a pericardium at the moment when a heart extends most.SOLUTION: A guide device 1 includes: a cylindrical puncture needle 2 having a through-hole penetrating in the longitudinal direction, and having a point 2a at one end an outer cylindrical part 3 movably containing the puncture needle 2 in the longitudinal direction, and having a tip opening 3a retracting the point 2a of the puncture needle 2 and locking means 4 fixing the longitudinal movement of the puncture needle 2 to the outer cylindrical part 3 while the point 2a of the puncture needle 2 is projected from the tip opening 3a to the outside, and alternatively, releasing the fixation when the force in the direction intersecting with a longitudinal axis acts on the point 2a of the puncture needle 2.
