A method of manufacturing a display panel, comprising: preparing a work substrate that includes a mother substrate that includes a plurality of cell areas, a light emitting element layer (DP-EDL) formed in each of the cell areas, and an encapsulation layer formed in each cell area; disposing a plurality of protective films in the cell areas, respectively, that cover the light emitting element layer (DP-EDL) and the encapsulation layer; cutting the work substrate along cutting lines (CL1-1, CL1-2, CL2-1, CL2-2) at an outer side of the protective films of at least one cell area wherein at least one preliminary display panel (P-DP) is formed; grinding side surfaces (SS1, SS2, SS3, SS4) of the at least one preliminary display panel (P-DP); and removing the protective film from the at least one ground preliminary display panel (P-DP) wherein at least one display panel is formed, wherein grinding side surfaces (SS1, SS2, SS3, SS4) of the at least one preliminary display panel (P-DP) comprises: grinding a straight-line-shaped portion (SLP1, SLP2, SLP3, SLP4) of the side surfaces (SS1, SS2, SS3, SS4) using a first grinding process, wherein the straight-line-shaped portion (SLP1, SLP2, SLP3, SLP4) has a straight line shape; and grinding a curved-surface-shaped portion (SMP1, SMP2, SMP3, SMP4) of the side surfaces (SS 1, SS2, SS3, SS4) using a second grinding process different from the first grinding process, wherein the curved-surface-shaped portion (SMP1, SMP2, SMP3, SMP4) has a curved shape and includes a first curved-line grind surface provided at a front surface edge of the at least one preliminary display panel (P-DP) and a second curved-line grind surface provided at a rear surface edge of the at least one preliminary display panel (P-DP), wherein the straight-line-shaped portion (SLP1, SLP2, SLP3, SLP4) includes a straight-line grind surface (SGS1-1, SGS1-2) on at least one of the front surface edge and the rear surface edge of the at least one preliminary display panel (P-DP), the width of the straight-line grind surface (SGS1-1, SGS1-2) is less than the width of the first and second curved-line grind surfaces (CGS1, CGS2) of the curved-surface-shaped portion (SMP1, SMP2, SMP3, SMP4). preparing a work substrate that includes a mother substrate that includes a plurality of cell areas, a light emitting element layer (DP-EDL) formed in each of the cell areas, and an encapsulation layer formed in each cell area; disposing a plurality of protective films in the cell areas, respectively, that cover the light emitting element layer (DP-EDL) and the encapsulation layer; cutting the work substrate along cutting lines (CL1-1, CL1-2, CL2-1, CL2-2) at an outer side of the protective films of at least one cell area wherein at least one preliminary display panel (P-DP) is formed; grinding side surfaces (SS1, SS2, SS3, SS4) of the at least one preliminary display panel (P-DP); and removing the protective film from the at least one ground preliminary display panel (P-DP) wherein at least one display panel is formed, wherein grinding side surfaces (SS1, SS2, SS3, SS4) of the at least one preliminary display panel (P-DP) comprises: grinding a straight-line-shaped portion (SLP1, SLP2, SLP3, SLP4) of the side surfaces (SS1, SS2, SS3, SS4) using a first grinding process, wherein the straight-line-shaped portion (SLP1, SLP2, SLP3, SLP4) has a straight line shape; and grinding a curved-surface-shaped portion (SMP1, SMP2, SMP3, SMP4) of the side surfaces (SS 1, SS2, SS3, SS4) using a second grinding process different from the first grinding process, wherein the curved-surface-shaped portion (SMP1, SMP2, SMP3, SMP4) has a curved shape and includes a first curved-line grind surface provided at a front surface edge of the at least one preliminary display panel (P-DP) and a second curved-line grind surface provided at a rear surface edge of the at least one preliminary display panel (P-DP), wherein the straight-line-shaped portion (SLP1, SLP2, SLP3, SLP4) includes a straight-line grind surface (SGS1-1, SGS1-2) on at least one of the front surface edge and the rear surface edge of the at least one preliminary display panel (P-DP), the width of the straight-line grind surface (SGS1-1, SGS1-2) is less than the width of the first and second curved-line grind surfaces (CGS1, CGS2) of the curved-surface-shaped portion (SMP1, SMP2, SMP3, SMP4). grinding a straight-line-shaped portion (SLP1, SLP2, SLP3, SLP4) of the side surfaces (SS1, SS2, SS3, SS4) using a first grinding process, wherein the straight-line-shaped portion (SLP1, SLP2, SLP3, SLP4) has a straight line shape; and grinding a curved-surface-shaped portion (SMP1, SMP2, SMP3, SMP4) of the side surfaces (SS 1, SS2, SS3, SS4) using a second grinding process different from the first grinding process, wherein the curved-surface-shaped portion (SMP1, SMP2, SMP3, SMP4) has a curved shape and includes a first curved-line grind surface provided at a front surface edge of the at least one preliminary display panel (P-DP) and a second curved-line grind surface provided at a rear surface edge of the at least one preliminary display panel (P-DP), wherein the straight-line-shaped portion (SLP1, SLP2, SLP3, SLP4) includes a straight-line grind surface (SGS1-1, SGS1-2) on at least one of the front surface edge and the rear surface edge of the at least one preliminary display panel (P-DP), the width of the straight-line grind surface (SGS1-1, SGS1-2) is less than the width of the first and second curved-line grind surfaces (CGS1, CGS2) of the curved-surface-shaped portion (SMP1, SMP2, SMP3, SMP4).