Provided is an exhaust-treatment device for a diesel engine, said device being capable of suppressing engine noise. In a first stage P1 of an exhaust-temperature-raising process, a target engine speed is set to a prescribed first target speed R1 and an intake throttle valve 41 is set to a prescribed first degree of opening O1. In a second stage P2, the target engine speed is maintained at the first target speed R1 and the intake throttle valve 41 is set to a position more closed than the first degree of opening O1. When a set duration T2 for the second stage P2 has come to an end, the intake throttle valve 41 is at a second degree of opening O2, which is maintained in third and subsequent stages P3/P4. In said third and subsequent stages P3/P4, as a set duration T3/T4 for each stage P3/P4 passes, the target engine speed is updated to a target speed R2/R3 higher than the target speed R1/R2 during the immediately prior stage P2/P3, and the temperature of DPF1 upstream exhaust gas 12 is increased.