A valve opening/closing timing control device comprising: a driving-side rotational member adapted to rotate synchronously with a crankshaft in an internal combustion engine; a driven-side rotational member disposed coaxially with the driving-side rotational member and adapted to rotate synchronously with a camshaft for opening and closing a valve in the internal combustion engine; a fluid pressure chamber formed by the driving-side rotational member and the driven-side rotational member; a partitioning portion provided in at least one of the driving-side rotational member and the driven-side rotational member so as to partition the fluid pressure chamber into an advance chamber and a retard chamber; and a projecting and retracting mechanism having a hole portion formed in one of the driving-side rotational member and the driven-side rotational member, a cylindrical sleeve accommodated in the hole portion, a projecting and retracting member accommodated in the sleeve and capable of projecting and retracting with respect to the other of the driving-side rotational member and the driven-side rotational member, and a fitting hole formed in the other of the driving-side rotational member and the driven-side rotational member such that the projecting and retracting member can be fitted to the fitting hole when the projecting and retracting member projects, the projecting and retracting mechanism constraining a relative rotational phase of the driven-side rotational member with respect to the driving-side rotational member at a predetermined phase when the projecting and retracting member is fitted to the fitting hole, wherein when the projecting and retracting member retracts from the fitting hole, an end face of the projecting and retracting member on a side opposite to a side facing the fitting hole comes into surface contact with a bottom surface of the hole portion, characterized in that the valve opening/closing timing control device further comprises a plurality of first chamfered surfaces formed dispersedly in a circumferential direction at an inner-circumferential corner of an end of the sleeve on a side opposite to a side facing the fitting hole. a driving-side rotational member adapted to rotate synchronously with a crankshaft in an internal combustion engine; a driven-side rotational member disposed coaxially with the driving-side rotational member and adapted to rotate synchronously with a camshaft for opening and closing a valve in the internal combustion engine; a fluid pressure chamber formed by the driving-side rotational member and the driven-side rotational member; a partitioning portion provided in at least one of the driving-side rotational member and the driven-side rotational member so as to partition the fluid pressure chamber into an advance chamber and a retard chamber; and a projecting and retracting mechanism having a hole portion formed in one of the driving-side rotational member and the driven-side rotational member, a cylindrical sleeve accommodated in the hole portion, a projecting and retracting member accommodated in the sleeve and capable of projecting and retracting with respect to the other of the driving-side rotational member and the driven-side rotational member, and a fitting hole formed in the other of the driving-side rotational member and the driven-side rotational member such that the projecting and retracting member can be fitted to the fitting hole when the projecting and retracting member projects, the projecting and retracting mechanism constraining a relative rotational phase of the driven-side rotational member with respect to the driving-side rotational member at a predetermined phase when the projecting and retracting member is fitted to the fitting hole,