To reduce time for detecting resonance conditions of a droplet ejection head.

A method for detecting resonance conditions of a droplet ejection head that discharges functional liquid from a nozzle in communication with a pressure chamber by resonating the functional liquid in the pressure chamber by giving a periodic external force to the pressure chamber in which the functional liquid is contained includes: an oscillation generating step of generating free oscillation of the functional liquid on a liquid surface at a discharge port of the nozzle without discharging the functional liquid from the nozzle by giving an instant external force to the pressure chamber in which the functional liquid is contained; and a frequency detecting step of detecting frequency of the free oscillation as frequency of the periodic external force based on a temporal response of a position on the liquid surface of the functional liquid that freely oscillates.