A liquid cartridge (30; 230; 330; 430; 530; 630; 730) movable relative to a printer in a front-rear direction (51, 52) crossing an up-down direction (53, 54) along a gravitational direction to be attached to a printer in an attached posture, the liquid cartridge (30; 230; 330; 430; 530; 630; 730) comprising: a cartridge case (35; 633) defining therein a liquid storage chamber, the cartridge case (35; 633) having a front surface; a liquid supply portion protruding frontward from the front surface of the cartridge case (35; 633) and configured to supply liquid stored in the liquid storage chamber to an outside; a circuit board (64; 564; 664) comprising an electrode group (65; 565) comprising at least three electrodes (65A, 65B, 65C), the at least three electrodes (65A, 65B, 65C) facing upward and being exposed to the outside in the attached posture; a plate member (67; 767) extending in the front-rear direction (51, 52) and positioned rearward of the electrode group (65; 565) in the attached posture; and a residual-amount detecting portion (59, 62; 131, 132) positioned upward relative to the electrode group (65; 565) and rearward of the plate member (67; 767) in the attached posture, the residual-amount detecting portion (59, 62; 131, 132) being configured to change a state of incident light according to an amount of the liquid stored in the liquid storage chamber, the residual-amount detecting portion (59, 62; 131, 132) comprising an optical access portion (60; 132) on which light traveling in a left-right direction (55, 56) crossing the up-down direction (53, 54) and the front-rear direction (51, 52) is incident in the attached posture, characterized in that the plate member (67; 767) is pivotally movable about an axis (axis of 68) extending in the left-right direction (55, 56) between: a first posture in which a portion of the plate member (67; 767) is positioned upward relative to the optical access portion (60; 132); and a second posture in which the plate member (67; 767) is positioned downward relative to the optical access portion (60; 132), the plate member (67; 767) in the second posture being positioned rearward relative to the plate member (67; 767) in the first posture, and wherein the plate member (67; 767) in the first posture and the residual-amount detecting portion (59, 62; 131, 132) define a light transmissive region therebetween in the front-rear direction (51, 52), the light transmissive region having a light transmittance greater than a light transmittance of the plate member (67; 767). a cartridge case (35; 633) defining therein a liquid storage chamber, the cartridge case (35; 633) having a front surface; a liquid supply portion protruding frontward from the front surface of the cartridge case (35; 633) and configured to supply liquid stored in the liquid storage chamber to an outside; a circuit board (64; 564; 664) comprising an electrode group (65; 565) comprising at least three electrodes (65A, 65B, 65C), the at least three electrodes (65A, 65B, 65C) facing upward and being exposed to the outside in the attached posture; a plate member (67; 767) extending in the front-rear direction (51, 52) and positioned rearward of the electrode group (65; 565) in the attached posture; and a residual-amount detecting portion (59, 62; 131, 132) positioned upward relative to the electrode group (65; 565) and rearward of the plate member (67; 767) in the attached posture, the residual-amount detecting portion (59, 62; 131, 132) being configured to change a state of incident light according to an amount of the liquid stored in the liquid storage chamber, the residual-amount detecting portion (59, 62; 131, 132) comprising an optical access portion (60; 132) on which light traveling in a left-right direction (55, 56) crossing the up-down direction (53, 54) and the front-rear direction (51, 52) is incident in the attached posture, characterized in that the plate member (67; 767) is pivotally movable about an axis (axis of 68) extending in the left-right direction (55, 56) between: a first posture in which a portion of the plate member (67; 767) is positioned upward relative to the optical access portion (60; 132); and a second posture in which the plate member (67; 767) is positioned downward relative to the optical access portion (60; 132), the plate member (67; 767) in the second posture being positioned rearward relative to the plate member (67; 767) in the first posture, and a first posture in which a portion of the plate member (67; 767) is positioned upward relative to the optical access portion (60; 132); and a second posture in which the plate member (67; 767) is positioned downward relative to the optical access portion (60; 132), the plate member (67; 767) in the second posture being positioned rearward relative to the plate member (67; 767) in the first posture, and wherein the plate member (67; 767) in the first posture and the residual-amount detecting portion (59, 62; 131, 132) define a light transmissive region therebetween in the front-rear direction (51, 52), the light transmissive region having a light transmittance greater than a light transmittance of the plate member (67; 767).