A valve opening/closing timing control device, comprising: a driving rotating body that rotates in synchronization with a crankshaft of an internal combustion engine; a driven rotating body that is located on an inner circumference side of the driving rotating body coaxially with a rotational axis of the driving rotating body so as to be relatively rotatable, and that rotates in synchronization with a camshaft for opening/closing a valve of the internal combustion engine; a fluid pressure chamber that is formed between the driving rotating body and the driven rotating body; an advancing chamber and a retarding chamber that are formed by partitioning the fluid pressure chamber with a partitioning portion that is provided on an outer circumference side of the driven rotating body; an advancing channel that is formed in the driven rotating body and is in communication with the advancing chamber; a retarding channel that is formed in the driven rotating body and is in communication with the retarding chamber; and a phase control unit that controls a rotation phase of the driven rotating body relative to the driving rotating body by controlling supply and discharge of a pressurized fluid that circulates through the advancing channel and the retarding channel, wherein the driven rotating body has: a first member that is cylindrical and is provided with the partitioning portion; and a second member that is cylindrical, has a rotational axis that is the same as a rotational axis of the first member, and has a portion that overlaps an inner side of the first member at least in a radial direction of the first member, out of the radial direction of the first member and an axial direction, and the advancing channel and the retarding channel are formed to penetrate through a boundary between the first member and the second member after the first member and the second member have been installed, wherein a drilling operation on the first member and the second member is performed in one process, and wherein the advancing channel and the retarding channel are provided with an intrusive portion where the first member or the second member intrudes into the other of the first member and the second member from the boundary. a driving rotating body that rotates in synchronization with a crankshaft of an internal combustion engine; a driven rotating body that is located on an inner circumference side of the driving rotating body coaxially with a rotational axis of the driving rotating body so as to be relatively rotatable, and that rotates in synchronization with a camshaft for opening/closing a valve of the internal combustion engine; a fluid pressure chamber that is formed between the driving rotating body and the driven rotating body; an advancing chamber and a retarding chamber that are formed by partitioning the fluid pressure chamber with a partitioning portion that is provided on an outer circumference side of the driven rotating body; an advancing channel that is formed in the driven rotating body and is in communication with the advancing chamber; a retarding channel that is formed in the driven rotating body and is in communication with the retarding chamber; and a phase control unit that controls a rotation phase of the driven rotating body relative to the driving rotating body by controlling supply and discharge of a pressurized fluid that circulates through the advancing channel and the retarding channel, wherein the driven rotating body has: a first member that is cylindrical and is provided with the partitioning portion; and a second member that is cylindrical, has a rotational axis that is the same as a rotational axis of the first member, and has a portion that overlaps an inner side of the first member at least in a radial direction of the first member, out of the radial direction of the first member and an axial direction, and the advancing channel and the retarding channel are formed to penetrate through a boundary between the first member and the second member after the first member and the second member have been installed, wherein a drilling operation on the first member and the second member is performed in one process, and wherein the advancing channel and the retarding channel are provided with an intrusive portion where the first member or the second member intrudes into the other of the first member and the second member from the boundary.