A dog clutch for an automated transmission, comprising: a rotary shaft rotatably connecting to one of an input shaft and an output shaft of the automated transmission and provided rotatably about an axial line; a clutch ring (23, 24) rotatably supported by the rotary shaft and rotatably connecting to the other of the input shaft and the output shaft; a hub fixed to the rotary shaft and arranged adjacent to the clutch ring (23, 24); a sleeve slidably engaging with the hub in a direction of the axial line, the sleeve including a spline, the spline including a plurality of first teeth (26a1) and a plurality of second teeth (26b1), a whole depth of each of the first teeth (26a1) being greater than a whole depth of each of the second teeth (26b1); an axial driving device moving the sleeve in the direction of the axial line; and a dog clutch portion (23a, 24a) provided at the clutch ring (23, 24) to project towards the sleeve, the dog clutch portion (23a, 24a) selectively engaging and disengaging relative to the spline formed at the sleeve when the sleeve moves in the direction of the axial line; the dog clutch portion including clutch forward teeth (23b1) of which an outer diameter is greater than an inner diameter of the first teeth (26a1) and smaller than an inner diameter of the second teeth (26b1), the teeth number of clutch forward teeth (23b1) being equal to the teeth number of first teeth (26a1), each of the clutch forward teeth (23b1) being formed at a position facing the first teeth (26a1) to extend from a front end surface (23a2) of the dog clutch portion to a rear end position (Pe) of the dog clutch portion, the dog clutch portion including clutch rearward teeth (23c1) engageable with tooth grooves (26c1) formed at the spline and formed to extend from a position retracted by a first predetermined distance from the front end surface (23a2) of the dog clutch portion to the rear end position (Pe) of the dog clutch portion, wherein at least two clutch rearward teeth (23c1) are arranged adjacent to each other, characterized in that each of the first teeth (26a1) is engageable with clutch tooth grooves (23d1) formed between the clutch forward tooth (23b1) and the clutch rearward tooth (23c1) and with clutch tooth grooves (23d1) formed between the clutch rearward teeth (23c1) adjacent to each other, and each of the second teeth (26b1) is engageable with clutch tooth grooves (23d1) formed between the clutch rearward teeth (23c1) adjacent to each other. a rotary shaft rotatably connecting to one of an input shaft and an output shaft of the automated transmission and provided rotatably about an axial line; a clutch ring (23, 24) rotatably supported by the rotary shaft and rotatably connecting to the other of the input shaft and the output shaft; a hub fixed to the rotary shaft and arranged adjacent to the clutch ring (23, 24); a sleeve slidably engaging with the hub in a direction of the axial line, the sleeve including a spline, the spline including a plurality of first teeth (26a1) and a plurality of second teeth (26b1), a whole depth of each of the first teeth (26a1) being greater than a whole depth of each of the second teeth (26b1); an axial driving device moving the sleeve in the direction of the axial line; and a dog clutch portion (23a, 24a) provided at the clutch ring (23, 24) to project towards the sleeve, the dog clutch portion (23a, 24a) selectively engaging and disengaging relative to the spline formed at the sleeve when the sleeve moves in the direction of the axial line; the dog clutch portion including clutch forward teeth (23b1) of which an outer diameter is greater than an inner diameter of the first teeth (26a1) and smaller than an inner diameter of the second teeth (26b1), the teeth number of clutch forward teeth (23b1) being equal to the teeth number of first teeth (26a1), each of the clutch forward teeth (23b1) being formed at a position facing the first teeth (26a1) to extend from a front end surface (23a2) of the dog clutch portion to a rear end position (Pe) of the dog clutch portion, the dog clutch portion including clutch rearward teeth (23c1) engageable with tooth grooves (26c1) formed at the spline and formed to extend from a position retracted by a first predetermined distance from the front end surface (23a2) of the dog clutch portion to the rear end position (Pe) of the dog clutch portion, wherein at least two clutch rearward teeth (23c1) are arranged adjacent to each other, characterized in that each of the first teeth (26a1) is engageable with clutch tooth grooves (23d1) formed between the clutch forward tooth (23b1) and the clutch rearward tooth (23c1) and with clutch tooth grooves (23d1) formed between the clutch rearward teeth (23c1) adjacent to each other, and each of the second teeth (26b1) is engageable with clutch tooth grooves (23d1) formed between the clutch rearward teeth (23c1) adjacent to each other.