To provide a constant mesh type transmission for a vehicle, preventing driving force from being shut off in shifting.

In this transmission for the vehicle, a power connecting/disconnecting device 38 provided in each of several pairs of shifting gears 36 of an automatic transmission 18 respectively includes: a first transmission passage 54 wherein a first one-way clutch 50 for transmitting power in the only direction from a counter gear 48 to a counter shaft 34 and a first dog clutch 52 are connected in series to each other; and a second transmission passage 60 wherein a second one-way clutch 56 for transmitting power in the only direction from the counter shaft 34 to the counter gear 48 and a second dog clutch 58 are connected in series to each other, in parallel with each other between the counter gear 48 and the counter shaft 34. With this structure, after releasing the first dog clutch 52 or the second dog clutch 58 forming a gear stage of the automatic transmission 18 before shifting, the first dog clutch 52 and the second dog clutch 58 for forming a gear stage after shifting are not engaged with each other, and as a result, the driving force is prevented from being shut off in shifting.