To obtain a modified aequorin modifier having high heat resistance, capable of storing in a liquid state without carrying out freeze drying and enabling simplification of storage method and prolongation of storage period in the case applied as reagent and examination medicine.

A modified apoaequrin is obtained by modifying at least one among lysine residues at 59 position and 182 position in amino acid sequence of wild type apoaequrin to other amino acid residue. A DNA codes the modified apoaequrin. This modified aequorin is obtained by using a protein and a modified aequorin complex is obtained by using the modified apoaequrin. A storage solution for storing the modified aequorin or the modified aequorin complex is provided.