An object of the present invention is to provide a test/diagnosis method for fertility which allows the estimation of the possibility of leading to pregnancy based on the ability of sperm to fuse with an egg and the identification of a cause of infertility; and a polynucleotide and a fertility testing kit which are used in the method. The present invention provides a test/diagnosis method for fertility, including a detection step of detecting on a biological sample taken from a human body, the presence or absence of a deletion or mutation in the human PGAM4 gene; a polynucleotide consisting of the base sequence of the human wild-type PGAM4 gene or the base sequence of the translation region of the gene, wherein the polynucleotide consists of a base sequence of 10-100 consecutive bases containing a mutated site of a single base substitution mutation having a high correlation with fertility; and a test kit for fertility comprising a reagent for detecting the presence or absence of a deletion or mutation in the human PGAM4 gene.