A light wave measurement apparatus comprising: a pulse separation unit to separate an input light wave into a fundamental pulse and a signal pulse; a time delay adjustment unit to adjust a time delay between the fundamental pulse and the signal pulse; a focusing unit to focus the fundamental pulse and the signal pulse, whose time delay is adjusted, on an ionization material; and an ionization yield measurement unit to measure an ionization yield from electrons and/or ions generated by the focused fundamental pulse and signal pulse, wherein the apparatus is configured to obtain a waveform of the input light wave from an ionization yield modulation changed by the signal pulse as a function of the time delay, characterized in that : the field strength of the signal pulse is 0.1% ~ 20% of that of the fundamental pulse, wherein the waveform of the input light wave is obtained from the ionization yield modulation calculated using the following equation: δN τ = N τ − N 0 = ∫ − ∞ + ∞ g t − τ E s t dt wherein δN(τ) is the ionization yield modulation changed by the signal pulse as a function of the time delay τ, N(τ) is the ionization yield measured as a function of the time delay τ, No is the ionization yield generated by only the fundamental pulse, g(t-τ) is a derivative value of an ionization rate with respect to the field strength of the fundamental pulse F(t-τ), and Es(t) is the waveform of the signal pulse, which is identical to the waveform of the input light wave. a pulse separation unit to separate an input light wave into a fundamental pulse and a signal pulse; a time delay adjustment unit to adjust a time delay between the fundamental pulse and the signal pulse; a focusing unit to focus the fundamental pulse and the signal pulse, whose time delay is adjusted, on an ionization material; and an ionization yield measurement unit to measure an ionization yield from electrons and/or ions generated by the focused fundamental pulse and signal pulse, wherein the apparatus is configured to obtain a waveform of the input light wave from an ionization yield modulation changed by the signal pulse as a function of the time delay, characterized in that : the field strength of the signal pulse is 0.1% ~ 20% of that of the fundamental pulse, wherein the waveform of the input light wave is obtained from the ionization yield modulation calculated using the following equation: δN τ = N τ − N 0 = ∫ − ∞ + ∞ g t − τ E s t dt wherein δN(τ) is the ionization yield modulation changed by the signal pulse as a function of the time delay τ, N(τ) is the ionization yield measured as a function of the time delay τ, No is the ionization yield generated by only the fundamental pulse, g(t-τ) is a derivative value of an ionization rate with respect to the field strength of the fundamental pulse F(t-τ), and Es(t) is the waveform of the signal pulse, which is identical to the waveform of the input light wave. the field strength of the signal pulse is 0.1% ~ 20% of that of the fundamental pulse, wherein the waveform of the input light wave is obtained from the ionization yield modulation calculated using the following equation: δN τ = N τ − N 0 = ∫ − ∞ + ∞ g t − τ E s t dt wherein δN(τ) is the ionization yield modulation changed by the signal pulse as a function of the time delay τ, N(τ) is the ionization yield measured as a function of the time delay τ, No is the ionization yield generated by only the fundamental pulse, g(t-τ) is a derivative value of an ionization rate with respect to the field strength of the fundamental pulse F(t-τ), and Es(t) is the waveform of the signal pulse, which is identical to the waveform of the input light wave. <EOS>