An electric power steering system comprising: a control device that computes an assist control amount (Ias*, Ias*sub) on the basis of a plurality of types of state amounts indicating a steering state of a steering system, and that controls a motor that serves as a generation source of an assist force to be applied to a steering mechanism of a vehicle on the basis of the assist control amount (Ias*, Ias*sub), characterized in that the control device executes a restriction process of setting a restriction value (IUL*, ILL*) with which a variation range of the assist control amount (Ias*) is restricted, individually for each of the state amounts, in accordance with each state amount used to compute the assist control amount (Ias*), and of restricting a value of the assist control amount (Ias*) using the restriction value (IUL*, ILL*), and a switching process for causing the assist control amount to transit from a first assist control amount (Ias*), which is the restricted assist control amount (Ias*), to a second assist control amount (Ias*sub), which is computed separately from the first assist control amount (Ias*), at a timing when a certain time elapses since the value of the assist control amount (Ias*) is restricted, and the control device varies a speed of transition from the first assist control amount (Ias*) to the second assist control amount (Ias*sub) on the basis of an internal state of the control device. a control device that computes an assist control amount (Ias*, Ias*sub) on the basis of a plurality of types of state amounts indicating a steering state of a steering system, and that controls a motor that serves as a generation source of an assist force to be applied to a steering mechanism of a vehicle on the basis of the assist control amount (Ias*, Ias*sub), characterized in that the control device executes a restriction process of setting a restriction value (IUL*, ILL*) with which a variation range of the assist control amount (Ias*) is restricted, individually for each of the state amounts, in accordance with each state amount used to compute the assist control amount (Ias*), and of restricting a value of the assist control amount (Ias*) using the restriction value (IUL*, ILL*), and a switching process for causing the assist control amount to transit from a first assist control amount (Ias*), which is the restricted assist control amount (Ias*), to a second assist control amount (Ias*sub), which is computed separately from the first assist control amount (Ias*), at a timing when a certain time elapses since the value of the assist control amount (Ias*) is restricted, and a restriction process of setting a restriction value (IUL*, ILL*) with which a variation range of the assist control amount (Ias*) is restricted, individually for each of the state amounts, in accordance with each state amount used to compute the assist control amount (Ias*), and of restricting a value of the assist control amount (Ias*) using the restriction value (IUL*, ILL*), and a switching process for causing the assist control amount to transit from a first assist control amount (Ias*), which is the restricted assist control amount (Ias*), to a second assist control amount (Ias*sub), which is computed separately from the first assist control amount (Ias*), at a timing when a certain time elapses since the value of the assist control amount (Ias*) is restricted, and the control device varies a speed of transition from the first assist control amount (Ias*) to the second assist control amount (Ias*sub) on the basis of an internal state of the control device.