A medical guide wire, comprising: a core that has a portion gradually tapered in diameter from a proximal end side to a distal end side; and an outer coil into which a distal end portion of the core is inserted, wherein the distal end side of the outer coil is connected with the distal end side of the distal end portion of the core to form a distal joining section, the proximal end side of the outer coil is connected with the proximal end side of the distal end portion of the core to form an outer coil proximal joining section, the distal end portion of the core either is a combined truncated cone formed by longitudinally connecting at least two truncated cones, or is formed by, from proximal to distal order, a combined truncated cone formed by longitudinally connecting at least two truncated cones and a constant diameter portion, the longitudinal length of each of the truncated cones (26A, 26B) decreases from proximal to distal order, when a maximum outer diameter of the combined truncated cone is defined as D0, a minimum outer diameter of the combined truncated cone is defined as D1, a total length of the combined truncated cone is defined as L, and an outer diameter at an arbitrary position X, which is located from a center in a cross section of the second maximum outer diameter D0 to the distal end side of the combined truncated cone, is defined as Dm, and the arbitrary position X is within a range of 0 < X < L, the outer diameter Dm of the combined truncated cone satisfies the following relational expression: Dm > D 0 − D 0 − D 1 X / L; characterized in that the outer diameter ratio of each of the truncated cones (26A, 26B) is increased from proximal to distal order, wherein the outer diameter ratio of a given truncated cone (26A/26B) is calculated by dividing the maximum outer diameter at the proximal end side of said given truncated cone (26A/26B) by the minimum outer diameter of the distal end side of said given truncated cone (26A/26B). a core that has a portion gradually tapered in diameter from a proximal end side to a distal end side; and an outer coil into which a distal end portion of the core is inserted, the distal end side of the outer coil is connected with the distal end side of the distal end portion of the core to form a distal joining section, the proximal end side of the outer coil is connected with the proximal end side of the distal end portion of the core to form an outer coil proximal joining section, the distal end portion of the core either is a combined truncated cone formed by longitudinally connecting at least two truncated cones, or is formed by, from proximal to distal order, a combined truncated cone formed by longitudinally connecting at least two truncated cones and a constant diameter portion, is a combined truncated cone formed by longitudinally connecting at least two truncated cones, or is formed by, from proximal to distal order, a combined truncated cone formed by longitudinally connecting at least two truncated cones and a constant diameter portion, the longitudinal length of each of the truncated cones (26A, 26B) decreases from proximal to distal order, when a maximum outer diameter of the combined truncated cone is defined as D0, a minimum outer diameter of the combined truncated cone is defined as D1, a total length of the combined truncated cone is defined as L, and an outer diameter at an arbitrary position X, which is located from a center in a cross section of the second maximum outer diameter D0 to the distal end side of the combined truncated cone, is defined as Dm, and the arbitrary position X is within a range of 0 < X < L, the outer diameter Dm of the combined truncated cone satisfies the following relational expression: Dm > D 0 − D 0 − D 1 X / L; characterized in that the outer diameter ratio of each of the truncated cones (26A, 26B) is increased from proximal to distal order, wherein the outer diameter ratio of a given truncated cone (26A/26B) is calculated by dividing the maximum outer diameter at the proximal end side of said given truncated cone (26A/26B) by the minimum outer diameter of the distal end side of said given truncated cone (26A/26B).