An electronic apparatus , comprising: a housing comprising: a bottom plate ; and a plurality of side plates perpendicular to the bottom plate , at least one side plate among the plurality of side plates comprising a protrusion protruding toward an inside of the housing ; a first substrate parallel with the bottom plate ; and at least one substrate module standing upright on the first substrate , the at least one substrate module comprising: a second substrate ; and a substrate fixing member to which the second substrate is fixed, the substrate fixing member comprising a hole engaged with the protrusion of the at least one side plate ; wherein the first substrate comprises a first connector , wherein the second substrate comprises a second connector connected to the first connector , and wherein the hole comprises an abutting portion abutting on a side surface of the protrusion with the first connector and the second connector connected to each other; and wherein with the abutting portion of the hole abutting on the side surface of the protrusion , the substrate fixing member is fixed with a screw to the bottom plate and at least one side plate among the plurality of side plates ; wherein the hole has a width within which movement of the protrusion in a direction perpendicular to the second substrate is restricted, and wherein the hole has a length greater than the width in a direction perpendicular to the first substrate . a housing comprising: a bottom plate ; and a plurality of side plates perpendicular to the bottom plate , at least one side plate among the plurality of side plates comprising a protrusion protruding toward an inside of the housing ; a bottom plate ; and a plurality of side plates perpendicular to the bottom plate , at least one side plate among the plurality of side plates comprising a protrusion protruding toward an inside of the housing ; a first substrate parallel with the bottom plate ; and at least one substrate module standing upright on the first substrate , the at least one substrate module comprising: a second substrate ; and a substrate fixing member to which the second substrate is fixed, the substrate fixing member comprising a hole engaged with the protrusion of the at least one side plate ; a second substrate ; and a substrate fixing member to which the second substrate is fixed, the substrate fixing member comprising a hole engaged with the protrusion of the at least one side plate ; wherein the first substrate comprises a first connector , wherein the second substrate comprises a second connector connected to the first connector , and wherein the hole comprises an abutting portion abutting on a side surface of the protrusion with the first connector and the second connector connected to each other; and wherein with the abutting portion of the hole abutting on the side surface of the protrusion , the substrate fixing member is fixed with a screw to the bottom plate and at least one side plate among the plurality of side plates ; wherein the hole has a width within which movement of the protrusion in a direction perpendicular to the second substrate is restricted, and wherein the hole has a length greater than the width in a direction perpendicular to the first substrate . <EOS>