A fuel injection control apparatus in an internal combustion engine having a plurality of cylinders, comprising: a fuel injection device for injecting fuel into the cylinders; a crank angle detector including a signal rotor, the signal rotor having: a plurality of tooth portions aligned along a circumferential direction with constant angular spacing; and a tooth missing portion arranged over an angular range larger than alignment spacing of the tooth portions, wherein the crank angle detector, in accordance with a rotation of the signal rotor, outputs a signal corresponding to each tooth portion and a signal corresponding to the tooth missing portion; a timer for measuring an inter-signal time period, which is a time period from when the crank angle detector outputs the signal corresponding to the tooth portion to when the crank angle detector outputs a signal corresponding to a subsequent tooth portion; and a control unit which uses the signal outputted from the crank angle detector to obtain a fuel injection timing, and according to the obtained fuel injection timing, causes the fuel injection device to start a fuel injection, wherein the control unit defines a reference tooth portion out of the tooth portions and the tooth missing portion, and sets, as the fuel injection timing, a point of time at which a predetermined standby time period, which is calculated based on the signal of the previous injection cycle, has elapsed from a point of time at which the reference tooth portion is detected, wherein the control unit recognizes a tooth missing zone based on the signal corresponding to the tooth missing portion and determines whether the fuel injection timing is set in a specific section that is the tooth missing zone other than a head section which is equivalent to a section of one piece of a normal tooth portion from a leading end of the tooth missing portion, and wherein, when the fuel injection timing is set in a section other than the specific section, the control unit sets, as the predetermined standby time period, a remaining time period shorter than one inter-signal time period, and wherein, when the fuel injection timing is set in the specific section, the control unit sets, as the predetermined standby time, a time period obtained by adding a number of inter-signal time periods equivalent to the number of missing teeth of the tooth missing portion to the remaining time period shorter than the one inter-signal time period. a fuel injection device for injecting fuel into the cylinders; a crank angle detector including a signal rotor, the signal rotor having: a plurality of tooth portions aligned along a circumferential direction with constant angular spacing; and a tooth missing portion arranged over an angular range larger than alignment spacing of the tooth portions, wherein the crank angle detector, in accordance with a rotation of the signal rotor, outputs a signal corresponding to each tooth portion and a signal corresponding to the tooth missing portion; a timer for measuring an inter-signal time period, which is a time period from when the crank angle detector outputs the signal corresponding to the tooth portion to when the crank angle detector outputs a signal corresponding to a subsequent tooth portion; and a control unit which uses the signal outputted from the crank angle detector to obtain a fuel injection timing, and according to the obtained fuel injection timing, causes the fuel injection device to start a fuel injection, wherein the control unit defines a reference tooth portion out of the tooth portions and the tooth missing portion, and sets, as the fuel injection timing, a point of time at which a predetermined standby time period, which is calculated based on the signal of the previous injection cycle, has elapsed from a point of time at which the reference tooth portion is detected, wherein the control unit recognizes a tooth missing zone based on the signal corresponding to the tooth missing portion and determines whether the fuel injection timing is set in a specific section that is the tooth missing zone other than a head section which is equivalent to a section of one piece of a normal tooth portion from a leading end of the tooth missing portion, and wherein, when the fuel injection timing is set in a section other than the specific section, the control unit sets, as the predetermined standby time period, a remaining time period shorter than one inter-signal time period, and wherein, when the fuel injection timing is set in the specific section, the control unit sets, as the predetermined standby time, a time period obtained by adding a number of inter-signal time periods equivalent to the number of missing teeth of the tooth missing portion to the remaining time period shorter than the one inter-signal time period.