A vehicular discharge lamp, comprising: a lamp body that has an outer tube, an arc tube arranged inside the outer tube, and a pair of electrodes arranged inside the arc tube; a first lead wire and a second lead wire that are respectively connected to the pair of electrodes, and of which end portions on sides that are opposite sides connected to the pair of electrodes are respectively provided as power supply terminal portions (24a,25a); a plug that is formed from a resin material, and has a first terminal cover portion and a second terminal cover portion that respectively cover the power supply terminal portions (24a,25a) of the pair of lead wires (24,25) in a state of close contact therewith from an outer circumferential side; a case body, to which the plug is joined, inside which the first terminal cover portion and the second terminal cover portion are arranged; and a starting device that is arranged inside the case body, and applies a starting voltage to the power supply terminal portion when starting the lamp body, wherein a gap is formed between the first terminal cover portion and the second terminal cover portion in a direction orthogonal to an optical axis of light radiated from the lamp body, and a partition is provided on the case body and arranged in the gap, and separates the first terminal cover portion and the second terminal cover portion, characterized in that a support wall portion and a retainer wall portion, each generally shaped as a cylinder extending in the optical axis direction, are provided on the case body, the support wall portion being provided on a cover portion of the case body and the retainer wall portion being provided on a case portion of the case body, and the first terminal cover portion is inserted into the support wall portion, and the second terminal cover portion is inserted into the retainer wall portion. a lamp body that has an outer tube, an arc tube arranged inside the outer tube, and a pair of electrodes arranged inside the arc tube; a first lead wire and a second lead wire that are respectively connected to the pair of electrodes, and of which end portions on sides that are opposite sides connected to the pair of electrodes are respectively provided as power supply terminal portions (24a,25a); a plug that is formed from a resin material, and has a first terminal cover portion and a second terminal cover portion that respectively cover the power supply terminal portions (24a,25a) of the pair of lead wires (24,25) in a state of close contact therewith from an outer circumferential side; a case body, to which the plug is joined, inside which the first terminal cover portion and the second terminal cover portion are arranged; and a starting device that is arranged inside the case body, and applies a starting voltage to the power supply terminal portion when starting the lamp body, wherein a gap is formed between the first terminal cover portion and the second terminal cover portion in a direction orthogonal to an optical axis of light radiated from the lamp body, and a partition is provided on the case body and arranged in the gap, and separates the first terminal cover portion and the second terminal cover portion, characterized in that a support wall portion and a retainer wall portion, each generally shaped as a cylinder extending in the optical axis direction, are provided on the case body, the support wall portion being provided on a cover portion of the case body and the retainer wall portion being provided on a case portion of the case body, and the first terminal cover portion is inserted into the support wall portion, and the second terminal cover portion is inserted into the retainer wall portion.