A developing cartridge comprising: a casing (10; 10A; 10B; 10C; 10E; 10F) for accommodating developer therein; a developing roller (30; 30F) rotatable about an axis extending in a first direction and positioned at one side of the casing (10; 10A; 10B; 10C; 10E; 10F) in a second direction; a storage medium (61; 61A; 61B; 61C; 61D; 61E; 61F) having an electric contact surface (611; 611A; 611B; 611C; 611D; 611E; 611F); and a holder (62; 62A; 62B; 62C; 62D; 62E; 62F) positioned at a side of the casing (10; 10A; 10B; 10C; 10E; 10F) in the first direction and movable relative to the casing (10; 10A; 10B; 10C; 10E; 10F) in the second direction between a first position and a second position, the holder (62; 62A; 62B; 62C; 62D; 62E; 62F) having an outer surface (620; 620A) at which the electric contact surface (611; 611A; 611B; 611C; 611D; 611E; 611F) is positioned and wherein the outer surface (620; 620A) is positioned at a side of the holder (62; 62A; 62B; 62C; 62D; 62E; 62F) in a third direction crossing the electric contact surface (611; 611A; 611B; 611C; 611D; 611E; 611F), and the outer surface (620; 620A) is movable relative to the casing (10; 10A; 10B; 10C; 10E; 10F) in the third direction, and a holder cover (45; 45F) positioned at the side of the casing (10; 10F) in the first direction, and covering at least a portion of the holder (62; 62F), wherein the holder cover (45; 45F) has one of a first recessed portion and a first through-hole (451a, 451b; 451F), and wherein the holder (62; 62F) includes a first boss (621a, 621b; 621aF) extending in the first direction and inserted into one of the first recessed portion and the first through-hole (451a, 451b; 451F), the first boss (621a, 621b; 621aF) being movable in the second direction relative to one of the first recessed portion and the first through-hole (451a, 451b; 451F) when the holder (62; 62F) moves relative to the casing (10; 10F) in the second direction between the first position and the second position, characterized in that said one of the first recessed portion and the first through-hole (451a, 451b; 451F) has a dimension in the second direction greater than a dimension of the first boss (621a, 621b; 621aF) in the second direction and the first through-hole (451a, 451b; 451F) has a dimension in the third direction greater than a dimension of the first boss (621a, 621b; 621aF) in the third direction. a casing (10; 10A; 10B; 10C; 10E; 10F) for accommodating developer therein; a developing roller (30; 30F) rotatable about an axis extending in a first direction and positioned at one side of the casing (10; 10A; 10B; 10C; 10E; 10F) in a second direction; a storage medium (61; 61A; 61B; 61C; 61D; 61E; 61F) having an electric contact surface (611; 611A; 611B; 611C; 611D; 611E; 611F); and a holder (62; 62A; 62B; 62C; 62D; 62E; 62F) positioned at a side of the casing (10; 10A; 10B; 10C; 10E; 10F) in the first direction and movable relative to the casing (10; 10A; 10B; 10C; 10E; 10F) in the second direction between a first position and a second position, the holder (62; 62A; 62B; 62C; 62D; 62E; 62F) having an outer surface (620; 620A) at which the electric contact surface (611; 611A; 611B; 611C; 611D; 611E; 611F) is positioned and wherein the outer surface (620; 620A) is positioned at a side of the holder (62; 62A; 62B; 62C; 62D; 62E; 62F) in a third direction crossing the electric contact surface (611; 611A; 611B; 611C; 611D; 611E; 611F), and the outer surface (620; 620A) is movable relative to the casing (10; 10A; 10B; 10C; 10E; 10F) in the third direction, and a holder cover (45; 45F) positioned at the side of the casing (10; 10F) in the first direction, and covering at least a portion of the holder (62; 62F), wherein the holder cover (45; 45F) has one of a first recessed portion and a first through-hole (451a, 451b; 451F), and wherein the holder (62; 62F) includes a first boss (621a, 621b; 621aF) extending in the first direction and inserted into one of the first recessed portion and the first through-hole (451a, 451b; 451F), the first boss (621a, 621b; 621aF) being movable in the second direction relative to one of the first recessed portion and the first through-hole (451a, 451b; 451F) when the holder (62; 62F) moves relative to the casing (10; 10F) in the second direction between the first position and the second position, characterized in that said one of the first recessed portion and the first through-hole (451a, 451b; 451F) has a dimension in the second direction greater than a dimension of the first boss (621a, 621b; 621aF) in the second direction and the first through-hole (451a, 451b; 451F) has a dimension in the third direction greater than a dimension of the first boss (621a, 621b; 621aF) in the third direction.