Abstract: A fuel level detector for an automobile fuel tank comprises a strut vertically provided within a fuel tank, a float slidably fitted around the strut and having a permanent magnet therein, a plurality of magnetic induction type reed switches slantedly disposed along the strut with a adequate distance between the adjacent reed switches, the length of which distance being defined such that the permanent magnet of the float always actuates two adjacent reed switches simultaneously, a plurality of resistances respectively connected to the plurality of reed switches for changing current value according to the reed switches which are actuated, a residual quantity warning means having an element of a luminous body which is connected between a ground and a predetermined reed switch among the plurality of reed switches, and a distance retention mechanism for keeping constant a distance between the predetermined reed switch and the bottom surface of the fuel tank and having a guide mounted to a base member for verticall