A double-faced clock having a device for adjusting time difference between two clock part. The double-faced clock comprising a first clock part containing a first gear group for operating hands of clock, a second clock part attached to a rear side of the first clock part which contains a second gear group similar to the first gear group, a driving shaft rotatably supported in the first and second clock parts and driven by a driving source which is mounted with a first driving gear engaging with any gear of the first gear group at its first end and which is mounted with a second driving gear engaging with any gear of the second gear group at its second end, and means for adjusting selectively time of one or both of the first and second clock parts.