The present invention provides: an inorganic porous carrier that can be used to increase the purity of nucleic acid in a production thereof, and that comprises a linker represented by general formula (1) and has mode diameter of 0.04 µm to 1 µm in a pore distribution as measured by mercury intrusion method, and the density of voids having an opening area of 0.0025 µm 2 or more as obtained by image analysis of the surface of the inorganic porous substance is 12 to 30 voids/µm 2 [in the formula (1), a bond marked with * represents a linkage to the oxygen atom in a silanol group of an inorganic porous substance; n is an integer of 1 etc.; R represents independently of each other an alkyl group containing 3 to 10 carbon atoms which may optionally have a substituent such as an alkoxy group etc.; and L represents a single bond; an alkylene group of 1 to 20 carbon atoms; or an alkylene group containing 2 to 20 carbon atoms which contains -CH 2 -Q-CH 2 - group wherein any group Q selected from a group consisting of -O- etc. is inserted into at least one of -CH 2 -CH 2 - group constituting the alkylene group]; and a method for preparing a nucleic acid using the same.