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 (S2007) 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 (S2007) 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 (S2007) 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 . <EOS>