In a rewritable compact disc having a wobble groove on a substrate, crystal and
amorphous states of a phase-change recording layer are an unrecorded/erased state
and a recorded state, respectively. When the recording layer is exposed to recording
light, amorphous marks assuming the recorded state are formed. At any of 2-, 4-
and 8-times velocities with respect to a reference velocity (1-times velocity)
whose linear velocity is 1.2-1.4 m/s, modulation m11 of a recorded signal
when the recording light of approximately 780 nm in wavelength irradiates the recording
layer via an optical system with NA=0.5 or 0.55 is 60-80%. A topmost level Rtop
of reflectivity of the eye pattern of the recorded signal during retrieving
at the 1-times velocity is 15-25%, and a jitter of the individual length of marks
and inter-mark spaces during retrieving at 1-times velocity is 35 ns or less. Recording
at 8-times or higher velocities is thereby realized without any risk of impairing
the read-compatibility with the conventional CD-RW specifications at least at 4-times velocity.