To provide a hydrotalcite having a large amount of silicate ions contained between layers, with its primary particles having a smaller average horizontal width and with little aggregation between the primary particles.SOLUTION: A hydrotalcite that fulfills (A) to (C) below and is represented by (Formula 1) below is provided. (M)(M)(OH)(A)mHO (Formula 1) (where Mis at least one divalent metal, Mis at least one trivalent metal, Ais a condensed silicate ion of n valence, 0.17≤x≤0.36, 0≤m≤10, and n is an integer of 1 or greater) (A) Molar ratio of Si to Mis 1.3 or greater； (B) Primary particles have an average horizontal width of 0.1 μm to 0.7 μm as determined by SEM method； (C) Monodispersion represented by the formula below is 50% or more: Monodispersion(%)=(average horizontal width of primary particles as determined by SEM method/average horizontal width of secondary particles as determined by laser diffraction method)×100.SELECTED DRAWING: Figure 1【課題】層間に含まれるケイ酸イオン量が多く、１次粒子の平均横幅が小さく、かつ１次粒子間の凝集が少ないハイドロタルサイトを提供する。【解決手段】以下の（Ａ）～（Ｃ）を満たす下記（式１）で表されるハイドロタルサイト。（Ｍ２＋）１－ｘ（Ｍ３＋）ｘ（ＯＨ）２（Ａｎ－）ｘ／ｎ・ｍＨ２Ｏ （式１）（ただし、式中Ｍ２＋は２価金属の少なくとも１種以上、Ｍ３＋は３価金属の少なくとも１種以上、Ａｎ－はｎ価の縮合ケイ酸イオンを表し、０．１７≦ｘ≦０．３６、０≦ｍ≦１０、ｎは１以上の整数である。）（Ａ）ＳｉのＭ３＋に対するモル比が１．３以上；（Ｂ）ＳＥＭ法による１次粒子の平均横幅が０．１μｍ以上０．７μｍ以下；（Ｃ）下記式で表わされる単分散度が５０％以上；単分散度（％）＝（ＳＥＭ法による１次粒子の平均横幅／レーザー回折法による２次粒子の平均横幅）×１００【選択図】図１
