An information sharing system, which enables information sharing between a plurality of users, through communication between a server and a plurality of terminal devices via a network, each terminal device of the plurality of terminal devices being used by a user from the plurality of users, wherein the terminal device includes: a post accepting unit accepting posting from a user; a post information transmitting unit transmitting post information on posting, which has been accepted by the post accepting unit, to the server; a first post information receiving unit receiving post information distributed from the server; a display processing unit performing processing to display post information, which has been received by the first post information receiving unit, at a display unit; an operation accepting unit accepting predetermined evaluation operation of the user related to post information displayed by the display processing unit; and an operation information transmitting unit transmitting operation information which has been accepted by the operation accepting unit, to the server, the server includes: a second post information receiving unit receiving post information transmitted from the terminal device; a post information distributing unit distributing post information, which has been received by the second post information receiving unit, to the terminal device used by a user included in a first group; an operation information receiving unit receiving operation information transmitted from the terminal device; and characterized in that the server includes, a post information determination unit determining whether post information related to the operation information received by the operation information receiving unit satisfies a predetermined condition or not on the basis of the operation information received by the operation information receiving unit, and post information, which has been determined by the post information determination unit as satisfying the predetermined condition, is made possible to be shared at the terminal device used by a user included in a second group, which is at least partially different from the first group, wherein the post information determination unit, based on the predetermined evaluation operation related to the post information by a user other than a user who posted the post information, determines if the post information satisfies the predetermined condition or not. a post accepting unit accepting posting from a user; a post information transmitting unit transmitting post information on posting, which has been accepted by the post accepting unit, to the server; a first post information receiving unit receiving post information distributed from the server; a display processing unit performing processing to display post information, which has been received by the first post information receiving unit, at a display unit; an operation accepting unit accepting predetermined evaluation operation of the user related to post information displayed by the display processing unit; and an operation information transmitting unit transmitting operation information which has been accepted by the operation accepting unit, to the server, the server includes: a second post information receiving unit receiving post information transmitted from the terminal device; a post information distributing unit distributing post information, which has been received by the second post information receiving unit, to the terminal device used by a user included in a first group; an operation information receiving unit receiving operation information transmitted from the terminal device; and characterized in that the server includes, a post information determination unit determining whether post information related to the operation information received by the operation information receiving unit satisfies a predetermined condition or not on the basis of the operation information received by the operation information receiving unit, and a second post information receiving unit receiving post information transmitted from the terminal device; a post information distributing unit distributing post information, which has been received by the second post information receiving unit, to the terminal device used by a user included in a first group; an operation information receiving unit receiving operation information transmitted from the terminal device; and a post information determination unit determining whether post information related to the operation information received by the operation information receiving unit satisfies a predetermined condition or not on the basis of the operation information received by the operation information receiving unit, and post information, which has been determined by the post information determination unit as satisfying the predetermined condition, is made possible to be shared at the terminal device used by a user included in a second group, which is at least partially different from the first group, wherein the post information determination unit, based on the predetermined evaluation operation related to the post information by a user other than a user who posted the post information, determines if the post information satisfies the predetermined condition or not.