A microscope comprising: a dark-field illumination system configured to irradiate dark-field illumination light to a preparation in which a specimen is encapsulated between a slide glass and a cover glass by using an encapsulant; an thumbnail imaging unit configured to take a dark-field thumbnail image of the preparation irradiated with the dark-field illumination light; and a region determiner configured to: detect a boundary between the encapsulant and air included between the slide glass and the cover glass based on the taken dark-field thumbnail image, wherein said boundary divides the dark-field thumbnail image into a closed region and an open region; compare an inside region of the closed region and an outside region and determine either one region as a region of interest and the other region as an air layer region; subdivide the dark-field thumbnail image into segments (ST205; ST305; ST405; ST505); and acquire a magnified image for each segment in turn, wherein the focus is set independently for each segment according to the following: if the region of interest and air layer region exist in mixed manner in the segment, then exclude the air layer region from the focus detection region (ST206-209; ST306-309; ST406, ST207-209; ST506, ST307-309), if only the region of interest exists in the segment, then focus without any regional specificity (ST210-213; ST310-313; ST410-413; ST510-513), and if the region of interest does not exist in the segment, then do not acquire a magnified image of that segment (ST211; ST311; ST211; ST311). a dark-field illumination system configured to irradiate dark-field illumination light to a preparation in which a specimen is encapsulated between a slide glass and a cover glass by using an encapsulant; an thumbnail imaging unit configured to take a dark-field thumbnail image of the preparation irradiated with the dark-field illumination light; and a region determiner configured to: detect a boundary between the encapsulant and air included between the slide glass and the cover glass based on the taken dark-field thumbnail image, wherein said boundary divides the dark-field thumbnail image into a closed region and an open region; compare an inside region of the closed region and an outside region and determine either one region as a region of interest and the other region as an air layer region; subdivide the dark-field thumbnail image into segments (ST205; ST305; ST405; ST505); and detect a boundary between the encapsulant and air included between the slide glass and the cover glass based on the taken dark-field thumbnail image, wherein said boundary divides the dark-field thumbnail image into a closed region and an open region; compare an inside region of the closed region and an outside region and determine either one region as a region of interest and the other region as an air layer region; subdivide the dark-field thumbnail image into segments (ST205; ST305; ST405; ST505); and acquire a magnified image for each segment in turn, wherein the focus is set independently for each segment according to the following: if the region of interest and air layer region exist in mixed manner in the segment, then exclude the air layer region from the focus detection region (ST206-209; ST306-309; ST406, ST207-209; ST506, ST307-309), if only the region of interest exists in the segment, then focus without any regional specificity (ST210-213; ST310-313; ST410-413; ST510-513), and if the region of interest does not exist in the segment, then do not acquire a magnified image of that segment (ST211; ST311; ST211; ST311). if the region of interest and air layer region exist in mixed manner in the segment, then exclude the air layer region from the focus detection region (ST206-209; ST306-309; ST406, ST207-209; ST506, ST307-309), if only the region of interest exists in the segment, then focus without any regional specificity (ST210-213; ST310-313; ST410-413; ST510-513), and if the region of interest does not exist in the segment, then do not acquire a magnified image of that segment (ST211; ST311; ST211; ST311).