An electronic device comprising: a housing including a front cover facing in a first direction and a rear cover facing in a second direction which is opposite to the first direction, the housing having a transparent area forming at least part of the front cover; a battery disposed within the housing; and a display device disposed within the housing and including a screen area exposed through the front cover, wherein the rear cover includes: a glass plate forming at least a portion of the electronic device; and a first coat layer disposed on a surface of the glass plate, the first coat layer at least partially including a network structure, and a second coat layer disposed on a surface of the first coat layer and including a shape corresponding to the network structure of the first coat layer, wherein the first coat layer includes a SiO 2 film, and wherein Si-O bonded units are at least 80% by-weight of mass of the first coat layer, wherein the first coat layer is obtainable by depositing inorganic polysilazane on at least one surface of the glass plate by wet spraying and, transforming the inorganic polysilazane into an SiO 2 film by application of overheated steam, performing a first hardening process by applying a temperature from 100 °C to 300 °C, and performing a second hardening process, which includes peroxide processing, wherein the surface roughness average (Ra) formed by the protrusion-and-depression shapes of the first coat layer is within a range of 100 nm to 300 nm, and wherein the first coat layer is hardened to at least 2200 MPa (as measured using a Berkovich indenter) by thermal processing (920, 925). a housing including a front cover facing in a first direction and a rear cover facing in a second direction which is opposite to the first direction, the housing having a transparent area forming at least part of the front cover; a battery disposed within the housing; and a display device disposed within the housing and including a screen area exposed through the front cover, wherein the rear cover includes: a glass plate forming at least a portion of the electronic device; and a first coat layer disposed on a surface of the glass plate, the first coat layer at least partially including a network structure, and a second coat layer disposed on a surface of the first coat layer and including a shape corresponding to the network structure of the first coat layer, wherein the first coat layer includes a SiO 2 film, and wherein Si-O bonded units are at least 80% by-weight of mass of the first coat layer, wherein the first coat layer is obtainable by depositing inorganic polysilazane on at least one surface of the glass plate by wet spraying and, transforming the inorganic polysilazane into an SiO 2 film by application of overheated steam, performing a first hardening process by applying a temperature from 100 °C to 300 °C, and performing a second hardening process, which includes peroxide processing, wherein the surface roughness average (Ra) formed by the protrusion-and-depression shapes of the first coat layer is within a range of 100 nm to 300 nm, and wherein the first coat layer is hardened to at least 2200 MPa (as measured using a Berkovich indenter) by thermal processing (920, 925). a glass plate forming at least a portion of the electronic device; and a first coat layer disposed on a surface of the glass plate, the first coat layer at least partially including a network structure, and a second coat layer disposed on a surface of the first coat layer and including a shape corresponding to the network structure of the first coat layer, wherein the first coat layer includes a SiO 2 film, and wherein Si-O bonded units are at least 80% by-weight of mass of the first coat layer, wherein the first coat layer is obtainable by depositing inorganic polysilazane on at least one surface of the glass plate by wet spraying and, transforming the inorganic polysilazane into an SiO 2 film by application of overheated steam, performing a first hardening process by applying a temperature from 100 °C to 300 °C, and performing a second hardening process, which includes peroxide processing, wherein the surface roughness average (Ra) formed by the protrusion-and-depression shapes of the first coat layer is within a range of 100 nm to 300 nm, and wherein the first coat layer is hardened to at least 2200 MPa (as measured using a Berkovich indenter) by thermal processing (920, 925).