In a rotational phase adjusting apparatus for adjusting a difference in rotational phase between a first element and a second element by controlling an engagement therebetween through a third element whose condition is set by a movement of a fourth element,an elastic member is arranged between the fourth element and the one of the first and second elements, and a brake generates a variable braking force to be applied to the fourth element so that a rotational positional relationship between the fourth element and the one of the first and second elements and a value of a force applicable from the fourth element to the third element are elastically variable in accordance with a value of the variable braking force.