A thin-section preparation method and device includes, in a one-blade set state where an entire first cutting blade is held by a holder, performing a first rough cutting step of rough cutting an embedded block using a first end region of the first cutting blade, and a first main cutting step of main cutting the embedded block using a second end region of the first cutting blade; and further includes, in a two-blade set state where the second end region of the first cutting blade and a first end region of a second cutting blade are held by the holder, performing a second rough cutting step of rough cutting the embedded block using the second end region of the first cutting blade, and a second main cutting step of main cutting the embedded block using the first end region of the second cutting blade.