To provide a gene expression amount reading system, an information terminal device, a gene expression amount reading method and a program, allowing easy reading of a gene expression amount inside a chromosome area.

This system displays a name of a gene included in a gene list received from a server device 100 on a dedicated viewer by use of the plug-in type dedicated viewer allowing direct start-up from an html file on a general-purpose Web browser. By allowing a user to operate the dedicated viewer, the dedicated viewer loads expression amount data when the user specifies the expression amount data on the gene stored in a client device 200, differentiates each the gene included in the gene list by a numerical value, a color, a pattern or the like according to the expression amount data, and outputs it.