To provide a handle adjusting mechanism for an infant vehicle mounted seat capable of safely and simply adjusting the direction of a handle for an infant carrier.

A pair of small-size second cylinders 42 integrally formed with an infant carrier is provided at both sides of the infant carrier arranged in a first cylinder 36. The second cylinders 42 have common center axes corresponding to the axis of rotation for rotating operation of a first cylinder 36 and an arm. A plurality of radial recesses 44, 46, 48, 50 are formed on the outer face of each second cylinder 42. A pair of connecting mechanism 54 disconnectable and operable with the first and second cylinders 36, 42 can lock the arm at any preset positions. Each locking mechanism includes a plate held inside the corresponding arm adjacent to the lower end with a pivotal pin 58. The plate has a finger 60 extending downward through a slot 38 and arrangeable to the specified recesses 44,... in the second cylinder 42.