In an electronic fuel injecting method and device for an internal combustion engine, wherein a basic injection time is obtained in accordance with an intake pressure of the engine and an engine rotational speed, and, during transition, the basic injection time is corrected in accordance with the operating conditions of the engine so as to determine a fuel injection time, out of three factors including an after-idle increase correction in which a correction value is increased to a predetermined level when an idle switch is turned "OFF", a throttle valve opening increase or decrease correction in which a correction value is obtained in accordance with a changing speed in opening of a throttle valve, and an intake pressure increase or decrease correction in which a correction value is obtained in accordance with a changing speed of the intake pressure, at least two factors are combined to obtain an increase correction value for acceleration or a decrease correction value for deceleration, and, when the factors are overlapped in value, the increase correction value for acceleration or the decrease correction value for deceleration is obtained through the maximal values or the minimal values thereof.