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 portion of the core has a distal small-diameter body and a combined truncated cone in order from the distal end side to the proximal end side, an outer coil distal end of the outer coil is connected with a core distal end of the distal small-diameter body to form a distal joining section, an outer coil proximal end of the outer coil is connected with a core proximal end of the distal end portion of the core to form an outer coil proximal joining section, the combined truncated cone is formed by longitudinally connecting at least two truncated cones, the longitudinal length of each of the truncated cones (26A, 26B) decreases from proximal to distal order, wherein 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 maximum outer diameter DO to the core distal end 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 > {D0-(D0-D1)X/L}, characterized in that: the outer diameter ratio of each of the truncated cones (26A, 26B) increases 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 (D2/D0) at the proximal end side of said given truncated cone (26A/26B) by the minimum outer diameter (D1/D2) 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, wherein the distal end portion of the core has a distal small-diameter body and a combined truncated cone in order from the distal end side to the proximal end side, an outer coil distal end of the outer coil is connected with a core distal end of the distal small-diameter body to form a distal joining section, an outer coil proximal end of the outer coil is connected with a core proximal end of the distal end portion of the core to form an outer coil proximal joining section, the combined truncated cone is formed by longitudinally connecting at least two truncated cones, the longitudinal length of each of the truncated cones (26A, 26B) decreases from proximal to distal order, wherein 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 maximum outer diameter DO to the core distal end 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 > {D0-(D0-D1)X/L}, characterized in that: the outer diameter ratio of each of the truncated cones (26A, 26B) increases 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 (D2/D0) at the proximal end side of said given truncated cone (26A/26B) by the minimum outer diameter (D1/D2) of the distal end side of said given truncated cone (26A/26B). the outer diameter ratio of each of the truncated cones (26A, 26B) increases 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 (D2/D0) at the proximal end side of said given truncated cone (26A/26B) by the minimum outer diameter (D1/D2) of the distal end side of said given truncated cone (26A/26B).