A truss plate detector preferably includes a first sensor array and a second sensor array. The first sensor array includes a plurality of sensors arranged to detect truss plates on a first side of a truss. A second sensor array preferably includes a plurality of sensors arranged to detect truss plates on a second side of a truss. A circuit is configured to receive signals from the first and second sensor arrays and to notify a user when one or more truss plates are missing or misaligned. For instance, the sensors in the first and second sensor arrays are preferably arranged opposite each other along the arrays. The truss plate detector can then be configured to notify a user when a sensor in the first sensor array detects a truss plate but neither a corresponding sensor nor an adjacent sensor in the second sensor array detects a truss plate. By providing a plurality of sensors in each array, the truss plate detector is capable of detecting a lateral position of truss plates on a truss being fed through the truss plate detector.