A biological information detection device comprising: an electrode pad that is able to detect a signal relating to biological information of a subject; a connector that is connectable to the electrode pad; and a cable that is connected to the connector and is able to transmit the signal, characterized in that the electrode pad and the connector are provided with fixing members (412, 33) that are attachable to and detachable from each other, respectively, the electrode pad includes an adhesive sheet that has an adhesive surface on one surface, a sensor part that is positioned on the adhesive surface and is able to detect the signal, a conductive gel sheet that is disposed to overlap the sensor part and is adherable, a signal line that is connected to the sensor part and extends to an outside of an outer peripheral edge of the conductive gel sheet, and a connection portion that is provided at a tip of the signal line and is connectable to the connector, the adhesive sheet has an opening portion that is formed to expose the connection portion to a surface opposite to the adhesive surface, and the fixing member (412, 33) is disposed at a position adjacent to the opening portion on the surface of the adhesive sheet opposite to the adhesive surface a connection direction of the connector is a surface direction of the adhesive sheet and is a direction different from an extension direction of the signal line from the sensor part to the outer peripheral edge of the conductive gel sheet, and in plan view of the adhesive sheet, a maximum dimension of an area in the adhesive sheet, in which the connector is provided, along the connection direction of the connector is equal to or smaller than a maximum dimension of an area, in which the conductive gel sheet is provided, along the connection direction of the connector. an electrode pad that is able to detect a signal relating to biological information of a subject; a connector that is connectable to the electrode pad; and a cable that is connected to the connector and is able to transmit the signal, characterized in that the electrode pad and the connector are provided with fixing members (412, 33) that are attachable to and detachable from each other, respectively, the electrode pad includes an adhesive sheet that has an adhesive surface on one surface, a sensor part that is positioned on the adhesive surface and is able to detect the signal, a conductive gel sheet that is disposed to overlap the sensor part and is adherable, a signal line that is connected to the sensor part and extends to an outside of an outer peripheral edge of the conductive gel sheet, and a connection portion that is provided at a tip of the signal line and is connectable to the connector, the adhesive sheet has an opening portion that is formed to expose the connection portion to a surface opposite to the adhesive surface, and the fixing member (412, 33) is disposed at a position adjacent to the opening portion on the surface of the adhesive sheet opposite to the adhesive surface a connection direction of the connector is a surface direction of the adhesive sheet and is a direction different from an extension direction of the signal line from the sensor part to the outer peripheral edge of the conductive gel sheet, and in plan view of the adhesive sheet, a maximum dimension of an area in the adhesive sheet, in which the connector is provided, along the connection direction of the connector is equal to or smaller than a maximum dimension of an area, in which the conductive gel sheet is provided, along the connection direction of the connector.