A medical guide wire comprising: a core having a large diameter on a proximal side and being tapered in diameter on a distal side toward a core distal end; an inner coil formed by helically winding at least one strand, the coil distal end of the inner coil being joined to the core distal end on an outer periphery of a core distal end portion at a distal joining section of the core, the coil proximal end of the inner coil being joined to the core distal end portion; an outer coil formed by helically winding at least one strand (8A, 8B), the outer coil being longer than the inner coil in a direction of the core, the coil distal end of the outer coil being joined to the core distal end at the distal joining section and the coil proximal end of the outer coil being joined to a constant diameter portion of the core in a state that the inner coil is joined to the core; an inner space wound portion provided on a distal side of the inner coil, a coil pitch (Pi) of the inner space wound portion being spaced; an outer space wound portion provided in the outer coil located outside of the inner space wound portion in a state that the inner and outer coils are joined to the core, a coil pitch (Po) of the outer space wound portion being spaced and differing from the coil pitch (Pi) of the inner space wound portion; characterised in that. the inner coil has a large constant diameter portion, a tapered middle portion, and a small constant diameter portion from the proximal side to the distal side and the outer coil has a large constant diameter portion, a tapered middle portion, and a small constant diameter portion from the proximal side to the distal side; the space wound portions are provided in coil distal end portions of the small constant diameter portions, respectively; and an outer diameter ratio (Di2/Di1) of the inner coil is greater than or equal to 1.15 and less than or equal to 2.80 and an outer diameter ratio (Do2/Do1) of the outer coil is greater than or equal to 1.10 and less than or equal to 1.80 and the outer diameter ratio (Di2/Di1) of the inner coil is greater than the outer diameter ratio (Do2/Do1) of the outer coil {(Di2/Di1) > (Do2/Do1)} where Di1 denotes an outer diameter of the small constant diameter portion of the inner coil, Di2 denotes an outer diameter of the large constant diameter portion of the inner coil, Do1 denotes an outer diameter of the small constant diameter portion of the outer coil, and Do2 denotes an outer diameter of the large constant diameter portion of the outer coil. a core having a large diameter on a proximal side and being tapered in diameter on a distal side toward a core distal end; an inner coil formed by helically winding at least one strand, the coil distal end of the inner coil being joined to the core distal end on an outer periphery of a core distal end portion at a distal joining section of the core, the coil proximal end of the inner coil being joined to the core distal end portion; an outer coil formed by helically winding at least one strand (8A, 8B), the outer coil being longer than the inner coil in a direction of the core, the coil distal end of the outer coil being joined to the core distal end at the distal joining section and the coil proximal end of the outer coil being joined to a constant diameter portion of the core in a state that the inner coil is joined to the core; an inner space wound portion provided on a distal side of the inner coil, a coil pitch (Pi) of the inner space wound portion being spaced; an outer space wound portion provided in the outer coil located outside of the inner space wound portion in a state that the inner and outer coils are joined to the core, a coil pitch (Po) of the outer space wound portion being spaced and differing from the coil pitch (Pi) of the inner space wound portion; characterised in that. the inner coil has a large constant diameter portion, a tapered middle portion, and a small constant diameter portion from the proximal side to the distal side and the outer coil has a large constant diameter portion, a tapered middle portion, and a small constant diameter portion from the proximal side to the distal side; the space wound portions are provided in coil distal end portions of the small constant diameter portions, respectively; and an outer diameter ratio (Di2/Di1) of the inner coil is greater than or equal to 1.15 and less than or equal to 2.80 and an outer diameter ratio (Do2/Do1) of the outer coil is greater than or equal to 1.10 and less than or equal to 1.80 and the outer diameter ratio (Di2/Di1) of the inner coil is greater than the outer diameter ratio (Do2/Do1) of the outer coil {(Di2/Di1) > (Do2/Do1)} where Di1 denotes an outer diameter of the small constant diameter portion of the inner coil, Di2 denotes an outer diameter of the large constant diameter portion of the inner coil, Do1 denotes an outer diameter of the small constant diameter portion of the outer coil, and Do2 denotes an outer diameter of the large constant diameter portion of the outer coil.