A valve opening and closing timing control apparatus comprising: a drive-side rotational body which rotates synchronously with a drive shaft of an internal combustion engine; a driven-side rotational body which is arranged at an inner side of the drive-side rotational body to be coaxial with an axis of the drive-side rotational body and rotates integrally with a camshaft for valve-opening-and-closing of the internal combustion engine; an intermediate lock mechanism which selectively switches between a lock state where displacement of a relative rotational phase of the driven-side rotational body relative to the drive-side rotational body is restrained by an operating oil supplied in an intermediate lock phase existing between a most advanced-angle phase of the relative rotational phase and a most retarded-angle phase of the relative rotational phase, and an unlock state where the lock state is released; and an electromagnetic valve at which a position of a spool is changed when a drive current applied to a drive source changes, and the operating oil is selectively supplied or discharged in accordance with the position of the spool such that the relative rotational phase is displaced in an advanced-angle direction or a retarded-angle direction, the electromagnetic valve selectively switching the supply and discharge of the operating oil to and from the intermediate lock mechanism, wherein a value of the drive current at which the lock state is switched to the unlock state and the unlock state is maintained is defined as a value of a boundary current, whose initial value is set previously, and at a time of predetermined operation of the internal combustion engine, a value of the drive current which differs, by a predetermined value, from a value of the drive current at a time when the unlock state was switched to the lock state due to the change of the drive current, and which maintains the unlock state is re-set as the value of the boundary current. a drive-side rotational body which rotates synchronously with a drive shaft of an internal combustion engine; a driven-side rotational body which is arranged at an inner side of the drive-side rotational body to be coaxial with an axis of the drive-side rotational body and rotates integrally with a camshaft for valve-opening-and-closing of the internal combustion engine; an intermediate lock mechanism which selectively switches between a lock state where displacement of a relative rotational phase of the driven-side rotational body relative to the drive-side rotational body is restrained by an operating oil supplied in an intermediate lock phase existing between a most advanced-angle phase of the relative rotational phase and a most retarded-angle phase of the relative rotational phase, and an unlock state where the lock state is released; and an electromagnetic valve at which a position of a spool is changed when a drive current applied to a drive source changes, and the operating oil is selectively supplied or discharged in accordance with the position of the spool such that the relative rotational phase is displaced in an advanced-angle direction or a retarded-angle direction, the electromagnetic valve selectively switching the supply and discharge of the operating oil to and from the intermediate lock mechanism, wherein a value of the drive current at which the lock state is switched to the unlock state and the unlock state is maintained is defined as a value of a boundary current, whose initial value is set previously, and at a time of predetermined operation of the internal combustion engine, a value of the drive current which differs, by a predetermined value, from a value of the drive current at a time when the unlock state was switched to the lock state due to the change of the drive current, and which maintains the unlock state is re-set as the value of the boundary current.