Spontaneous carrier lifetimes in InGaAsP/InP double heterostructure lasers emitting at1.3µm were experimentally determined from lasing delay time measarement. Various step-current superposed on bias current was applied to a laser diode with 20 µm-stripe geometry. The carrier lifetime apparently decreased with increasing bias current from 4-5 ns at non-biased state to2 ns at well biased state. This change in the measured lifetime was explained by considering the effect of junction capacitance. It was shown that the effect was almost removed by the application of bias current of more than1 kAcm-2. µm-1 and then the intrinsic lifetime was obtained. Deduced carrier lifetime well agreed with that estimated from relaxation oscillation measurement.