An arrangement having an attaching structure for attaching a service-plug comprising: a power source device, and said service-plug adapted for shutting off and conducting an electric circuit of a vehicle to said power source device, the attaching structure comprising: a floor metal plate constituting a bottom wall of a compartment of the vehicle and formed with an opening which faces the compartment; a metal plate disposed outside the vehicle under the floor metal plate and forming a cavity between the metal plate and the floor metal plate and adapted for covering the power source device, and including an attachment portion to which the service-plug is attached, the attachment portion being raised toward the opening in the cavity, and a sealing member for keeping the cavity liquid-tight disposed between the floor metal plate and the metal plate so as to surround the attachment portion; wherein the service-plug is detachably attached to the attachment portion so as to project toward the compartment through the opening, the power source device comprises a connector unit for connection to a further electric circuit that is lower in voltage than the above electric circuit and a plate member to which the service-plug and the connector unit are attached so as to be integrated with each other; and the service-plug is attached to the attachment portion in a state that the service-plug is integrated with the connector unit by the plate member. a power source device, and said service-plug adapted for shutting off and conducting an electric circuit of a vehicle to said power source device, the attaching structure comprising: a floor metal plate constituting a bottom wall of a compartment of the vehicle and formed with an opening which faces the compartment; a metal plate disposed outside the vehicle under the floor metal plate and forming a cavity between the metal plate and the floor metal plate and adapted for covering the power source device, and including an attachment portion to which the service-plug is attached, the attachment portion being raised toward the opening in the cavity, and a sealing member for keeping the cavity liquid-tight disposed between the floor metal plate and the metal plate so as to surround the attachment portion; a floor metal plate constituting a bottom wall of a compartment of the vehicle and formed with an opening which faces the compartment; a metal plate disposed outside the vehicle under the floor metal plate and forming a cavity between the metal plate and the floor metal plate and adapted for covering the power source device, and including an attachment portion to which the service-plug is attached, the attachment portion being raised toward the opening in the cavity, and a sealing member for keeping the cavity liquid-tight disposed between the floor metal plate and the metal plate so as to surround the attachment portion; wherein the service-plug is detachably attached to the attachment portion so as to project toward the compartment through the opening, the power source device comprises a connector unit for connection to a further electric circuit that is lower in voltage than the above electric circuit and a plate member to which the service-plug and the connector unit are attached so as to be integrated with each other; and the service-plug is attached to the attachment portion in a state that the service-plug is integrated with the connector unit by the plate member.