In an obstacle detection apparatus, a signal output unit is configured to output a signal if an obstacle meets at least one preset signal output condition. A condition setting unit is configured to set at least one element of the at least one signal output condition to a value in dependence on a user entry value. A misalignment detection unit is configured to detect misalignment of an axial direction of a sensor with a longitudinal direction of a vehicle carrying the apparatus. In the apparatus, an allowable range limiting unit is configured to, if a degree of misalignment exceeds a predetermined misalignment threshold, limit an allowable range of values of the at least one element of the at least one preset signal output condition so as to make the at least one preset signal output condition less prone to be met.