Disclosed is a torque converter in a vehicle, in which a torsional damper reduces a natural frequency and absorbs vibration energy in an anti-resonance state for enhancing a vibration isolation function. The torque converter in a vehicle includes a torsional damper including a retaining plate coupled to the piston, a plurality of springs arranged at the retaining plate for imparting elastic force in a circumferential direction, a driven plate coupled to a spline hub which acts as a reaction force on the springs and forwards driving power to a transmission, and an inertial lever arranged between the piston and the driven plate, the inertial lever including a fixed pivot coupling portion coupled to the piston with a fixed pivot and a movable pivot coupling portion coupled to the driven plate with a movable pivot.