The invention discloses an elevator landing door sill slotting device and method. The elevator landing door sill slotting device comprises a positioning assembly, a track support assembly, a transverse track, a track connecting piece, a longitudinal track and a fixing piece, all of which are sequentially connected from bottom to top. The track connecting piece is connected to the transverse trackin a sliding manner. The fixing piece is connected to the longitudinal track in a sliding manner. A vertical motor is fixed to the fixing piece. A rotation shaft of the vertical motor is connected with a slotting milling cutter. The two sides of the transverse track are movably sleeved with stroke limiting pieces, and the transverse movement of the track connecting piece is limited. The problem about direct slotting of the interior of an elevator landing door sill groove on the site is effectively solved, and a kidney-shaped groove hole with the hole diameter 12 mm x length 50 mm x depth 6 mm,and the problem that common foreign matter jams a landing door is effectively solved. The elevator fault rate is reduced, the technology process is simple, the automation degree is high, the production efficiency can be improved in a multiplied manner, the production cost is greatly reduced, and the elevator running quality is improved.