We study the p-adic (generalized) hypergeometric equations by using the theory of multiplicative convolution of arithmetic D-modules. As a result, we prove that the hypergeometric isocrystals with suitable rational parameters have a structure of overconvergent F -isocrystals. 0 Introduction. Katz [Ka, 5.3.1] discovered that the hypergeometric D-modules on A 1 C \{0} can be described as the multiplicative convolution of hypergeometric D-modules of rank one. Precisely speaking, Katz proved the statement (ii) in the following theorem (the statement (i) is trivial but put to compare with another theorem later).Convolution Theorem over C. Let α = (α 1 , . . . , α m ) and β = (β 1 , . . . , β n ) be two sequences of complex numbers and assume that α i −β j is not an integer for any i , j . Let Hyp(α;β) be the D-module on G m,C defined by the hypergeometric operatorThen, Hyp π (α; β) has the following properties.(i) If m = n, then Hyp π (α; β) has a structure of an overconvergent F -isocrystal on G m,k of rank max {m, n}. If m = n, then the restriction of Hyp π (α; β) to P 1 V \{0, 1, ∞} has a structure of an overconvergent F -isocrystal on G m,k \{1} of rank m.