1. An own-position estimation device comprising: one or more peripheral sensor mounted in a vehicle and configured to detect positions of landmarks present around the vehicle relative to the vehicle; one or more vehicle sensor configured to detect a movement amount of the vehicle; and a controller configured to: accumulate the positions of the landmarks relative to the vehicle detected by the one or more peripheral sensor as landmark position data by coordinates based on the movement amount detected by the one or more vehicle sensor; extract straight lines from the landmark position data accumulated at a plurality of times; select pieces of the landmark position data based on angles formed by intersecting ones of the extracted straight lines; store map information including positions of landmarks; and estimate a position of the vehicle by matching the selected pieces of the landmark position data and the positions of the landmarks in the map information.