A dialysis device comprising a dialysis fluid circuit for supplying a dialysis fluid to a dialyzer and a filter connected to the dialysis fluid circuit and for filtering the dialysis fluid, and configured to be controlled by control means, wherein: the filter includes a cylindrical housing arranged with a longitudinal direction vertically and accommodating a filter material therein, an introduction port provided on a lower part of the housing and introducing the dialysis fluid into an inside, a filtered fluid lead-out port provided on an upper part of the housing for leading out a filtered dialysis fluid having passed through the filter material in the dialysis fluid having been introduced through the introduction port, and an unfiltered fluid lead-out port provided on an upper part of the housing for leading out unfiltered fluid not having passed through the filter material in the dialysis fluid having been introduced through the introduction port; the dialysis fluid circuit includes an upstream-side flow path connected to the introduction port of the filter and causing the dialysis fluid to flow into the housing, a downstream-side flow path connected to the filtered fluid lead-out port of the filter and causing the filtered dialysis fluid to flow out from the inside of the housing, and a waste fluid flow path connected to the unfiltered fluid lead-out port and causing the unfiltered fluid to be discharged from the inside of the housing; and fluid suction means capable of suctioning the fluid inside the housing through the upstream-side flow path and gas inflow means for causing a gas to flow into the housing through at least either one of the waste fluid flow path and the downstream-side flow path are provided in the dialysis fluid circuit; and characterized in that the gas inflow means is configured to be opened by control of the control means, and the fluid suction means is configured to suction the fluid in the housing by control of the control means so as to discharge the fluid in the housing to an outside when the filter is to be removed from the dialysis fluid circuit by separating it from the upstream-side flow path, the downstream-side flow path, and the waste fluid flow path. the filter includes a cylindrical housing arranged with a longitudinal direction vertically and accommodating a filter material therein, an introduction port provided on a lower part of the housing and introducing the dialysis fluid into an inside, a filtered fluid lead-out port provided on an upper part of the housing for leading out a filtered dialysis fluid having passed through the filter material in the dialysis fluid having been introduced through the introduction port, and an unfiltered fluid lead-out port provided on an upper part of the housing for leading out unfiltered fluid not having passed through the filter material in the dialysis fluid having been introduced through the introduction port; the dialysis fluid circuit includes an upstream-side flow path connected to the introduction port of the filter and causing the dialysis fluid to flow into the housing, a downstream-side flow path connected to the filtered fluid lead-out port of the filter and causing the filtered dialysis fluid to flow out from the inside of the housing, and a waste fluid flow path connected to the unfiltered fluid lead-out port and causing the unfiltered fluid to be discharged from the inside of the housing; and fluid suction means capable of suctioning the fluid inside the housing through the upstream-side flow path and gas inflow means for causing a gas to flow into the housing through at least either one of the waste fluid flow path and the downstream-side flow path are provided in the dialysis fluid circuit; and characterized in that the gas inflow means is configured to be opened by control of the control means, and the fluid suction means is configured to suction the fluid in the housing by control of the control means so as to discharge the fluid in the housing to an outside when the filter is to be removed from the dialysis fluid circuit by separating it from the upstream-side flow path, the downstream-side flow path, and the waste fluid flow path.