Pest control device and volatile substance holder for use in same

A pest control device, comprising:

• a volatile substance holder, including a first and a second volatilization surfaces, said first volatilization surface holding a pest control component so that said pest control component can be volatilized into the air, and said second volatilization surface being able to hold a liquid so that said liquid can be volatilized into the air, where said pest control component and said liquid are volatile at ordinary temperature;
• and
• indicating means, including liquid supplying means and liquid containing means, said liquid supplying means supplying said liquid to said second volatilization surface of said volatile substance holder, and said liquid containing means containing said liquid to be supplied to said second volatilization surface via said liquid supplying means, wherein said indicating means indicates how much said pest control component to be volatilized from said first volatilization surface is left in said volatile substance holder by showing how much the liquid is left in said liquid containing means.