A trigger-type liquid dispenser comprising a dispenser main body fitted to a mouth of a container containing a liquid, a nozzle disposed on a downstream side of a flow path provided in the dispenser main body, and a pump that is actuated in response to operation of a trigger to pressure-feed the liquid contained in the container to the nozzle through the flow path, wherein the pump includes: a cylinder that has a coaxial double-wall configuration including an inner tubular wall and an outer tubular wall and that communicates with the flow path; a piston that is fitted displaceably between the inner tubular wall and the outer tubular wall in a direction extending along a center axis of the cylinder and that has a front-side end portion engaged with the trigger; a front-side sealing piece and a rear-side sealing piece that each are provided integrally in the piston and that each abut against an inner circumferential surface of the outer tubular wall in a liquid-tight manner; an outer-circumferential-side support portion that is provided integrally in the piston on a front side of the front-side sealing piece and that slidably abuts against the inner circumferential surface of the outer tubular wall; and an inner-circumferential-side support portion that is provided integrally on at least one of an outer circumferential surface of the inner tubular wall and an inner circumferential surface of the piston and that slidably abuts against another one of the outer circumferential surface of the inner tubular wall and the inner circumferential surface of the piston, and wherein the outer-circumferential-side support portion is provided with an annular cut-off portion that forms a gap between the outer-circumferential-side support portion and an outer circumferential surface of the piston, wherein the inner-circumferential-side support portion is configured by a plurality of projections that is disposed at an interval in a circumferential direction. a cylinder that has a coaxial double-wall configuration including an inner tubular wall and an outer tubular wall and that communicates with the flow path; a piston that is fitted displaceably between the inner tubular wall and the outer tubular wall in a direction extending along a center axis of the cylinder and that has a front-side end portion engaged with the trigger; a front-side sealing piece and a rear-side sealing piece that each are provided integrally in the piston and that each abut against an inner circumferential surface of the outer tubular wall in a liquid-tight manner; an outer-circumferential-side support portion that is provided integrally in the piston on a front side of the front-side sealing piece and that slidably abuts against the inner circumferential surface of the outer tubular wall; and an inner-circumferential-side support portion that is provided integrally on at least one of an outer circumferential surface of the inner tubular wall and an inner circumferential surface of the piston and that slidably abuts against another one of the outer circumferential surface of the inner tubular wall and the inner circumferential surface of the piston, and wherein the outer-circumferential-side support portion is provided with an annular cut-off portion that forms a gap between the outer-circumferential-side support portion and an outer circumferential surface of the piston, wherein the inner-circumferential-side support portion is configured by a plurality of projections that is disposed at an interval in a circumferential direction.