An indexable cutting tool with a cutting insert provided in a replaceable manner, the indexable cutting tool comprising: a body for holding the cutting insert; a lever having one end accommodated in a space provided in the cutting insert; and a pressing member for pressing the lever wherein the body has an insert fixing portion for placing the cutting insert, and the insert fixing portion being provided with a placement surface on which the cutting insert is placed and a side wall formed along the edge of the placement surface and abutting on a side surface of the cutting insert; wherein the cutting insert comprises a through hole formed between a first surface and a second surface that are opposite to each other, the through hole having: a first portion defining a first space adjacent to the first surface; a second portion adjacent to the second surface and defining a second space; and a constricted portion formed between the first portion and the second portion so as to connect the first space to the second space; wherein the one end of the lever is arranged at a bottom of the insert fixing portion so as to protrude from the placement surface of the insert fixing portion and be accommodated in the space defined by the second portion of the insert; and wherein the one end of the lever applies a clamping force to the cutting insert from the inside of the second portion of the through hole; characterised in that: the second space is larger than the first space; the pressing member is adapted for causing the lever to be inclined around a fulcrum on the lever so that the clamping force is applied to the lever; and a position where a pressing force of the pressing member is applied and a position of the fulcrum are defined such that the lever is inclined in a manner that the one end moves forward in a pressing direction by the pressing member. a body for holding the cutting insert; a lever having one end accommodated in a space provided in the cutting insert; and a pressing member for pressing the lever wherein the body has an insert fixing portion for placing the cutting insert, and the insert fixing portion being provided with a placement surface on which the cutting insert is placed and a side wall formed along the edge of the placement surface and abutting on a side surface of the cutting insert; wherein the cutting insert comprises a through hole formed between a first surface and a second surface that are opposite to each other, the through hole having: a first portion defining a first space adjacent to the first surface; a second portion adjacent to the second surface and defining a second space; and a constricted portion formed between the first portion and the second portion so as to connect the first space to the second space; wherein the one end of the lever is arranged at a bottom of the insert fixing portion so as to protrude from the placement surface of the insert fixing portion and be accommodated in the space defined by the second portion of the insert; and wherein the one end of the lever applies a clamping force to the cutting insert from the inside of the second portion of the through hole; characterised in that: the second space is larger than the first space; the pressing member is adapted for causing the lever to be inclined around a fulcrum on the lever so that the clamping force is applied to the lever; and a position where a pressing force of the pressing member is applied and a position of the fulcrum are defined such that the lever is inclined in a manner that the one end moves forward in a pressing direction by the pressing member. a first portion defining a first space adjacent to the first surface; a second portion adjacent to the second surface and defining a second space; and a constricted portion formed between the first portion and the second portion so as to connect the first space to the second space; wherein the one end of the lever is arranged at a bottom of the insert fixing portion so as to protrude from the placement surface of the insert fixing portion and be accommodated in the space defined by the second portion of the insert; and wherein the one end of the lever applies a clamping force to the cutting insert from the inside of the second portion of the through hole; characterised in that: the second space is larger than the first space; the pressing member is adapted for causing the lever to be inclined around a fulcrum on the lever so that the clamping force is applied to the lever; and a position where a pressing force of the pressing member is applied and a position of the fulcrum are defined such that the lever is inclined in a manner that the one end moves forward in a pressing direction by the pressing member. the second space is larger than the first space; the pressing member is adapted for causing the lever to be inclined around a fulcrum on the lever so that the clamping force is applied to the lever; and a position where a pressing force of the pressing member is applied and a position of the fulcrum are defined such that the lever is inclined in a manner that the one end moves forward in a pressing direction by the pressing member.