We present spatially-multiplexed fiducial markers with the framework of code division multiple access (CDMA), which is a technique in the field of communications. Since CDMA based multiplexing is robust to signal noise and interference, multiplexed markers can be demultiplexed under several image noises and transformation. With this framework, we explore the paradigm of multiple-input and multiple-output (MIMO) for fiducial markers so that the data capacity of markers can be improved and different users can receive different data from a multiplexed marker.