A fluid detection apparatus to detect quantity of a fluid having flowability and stored in a casing, the fluid detection apparatus comprising: an oscillator disposed outside the casing to output a frequency of an oscillation signal corresponding to a magnetic flux passing through a space near the oscillator; a vibrator made of material effecting the magnetic flux and disposed inside the casing, the vibrator facing the oscillator via a wall of the casing; a vibration trigger disposed inside the casing to vibrate the vibrator; and a processor to: acquire frequency-related information related to the frequency of the oscillation signal output from the oscillator periodically, the frequency-related information changeable depending on a vibration of the vibrator; detect the vibration of the vibrator based on a change of the frequency-related information; determine whether the vibrator vibrates at or above a sufficient level to enable an attenuation rate of the vibration of the vibrator to be calculated; calculate the attenuation rate of the vibration of the vibrator; and detect the quantity of the fluid in the casing based on (i) a result of the determination of whether the vibrator is vibrating at or above said level and (ii) the calculated attenuation rate of the vibration of the vibrator. an oscillator disposed outside the casing to output a frequency of an oscillation signal corresponding to a magnetic flux passing through a space near the oscillator; a vibrator made of material effecting the magnetic flux and disposed inside the casing, the vibrator facing the oscillator via a wall of the casing; a vibration trigger disposed inside the casing to vibrate the vibrator; and a processor to: acquire frequency-related information related to the frequency of the oscillation signal output from the oscillator periodically, the frequency-related information changeable depending on a vibration of the vibrator; detect the vibration of the vibrator based on a change of the frequency-related information; determine whether the vibrator vibrates at or above a sufficient level to enable an attenuation rate of the vibration of the vibrator to be calculated; calculate the attenuation rate of the vibration of the vibrator; and detect the quantity of the fluid in the casing based on (i) a result of the determination of whether the vibrator is vibrating at or above said level and (ii) the calculated attenuation rate of the vibration of the vibrator. acquire frequency-related information related to the frequency of the oscillation signal output from the oscillator periodically, the frequency-related information changeable depending on a vibration of the vibrator; detect the vibration of the vibrator based on a change of the frequency-related information; determine whether the vibrator vibrates at or above a sufficient level to enable an attenuation rate of the vibration of the vibrator to be calculated; calculate the attenuation rate of the vibration of the vibrator; and detect the quantity of the fluid in the casing based on (i) a result of the determination of whether the vibrator is vibrating at or above said level and (ii) the calculated attenuation rate of the vibration of the vibrator.