An intensity of light reflected on a phase-changing type of information recording medium is changed since unrecorded and recorded portions of the recording medium have different phase states so that reflectivities of the unrecorded and recorded portions are different from each other. Such an intensity change takes place in a very short time immediately after a recording pulse is irradiated onto the phase-changing type of information recording medium. In a recording and simultaneous verifying method of the phase-changing type of information recording medium, the change in intensity of light reflected on the phase-changing type of information recording medium is detected by using this light reflected simultaneously with a recording pulse irradiated onto the phase-changing type of information recording medium. It is confirmed if the information is correctly recorded by detecting the reflected light. Thus, this information can be recorded to the information recording medium and can be simultaneously verified.