Electronic element storing package and electronic device

An electronic element storing package comprising:

• a base including a wall body;
• a coaxial line located in the wall body;
• and
• a transmission line connected to the coaxial line on a side of the wall body,
• wherein
• the coaxial line includes a central conductor that is long in one direction, an outer peripheral conductor, and a dielectric that is located between the central conductor and the outer peripheral conductor,
• the dielectric has a first end face facing the transmission line,
• the wall body includes an opening leading to the first end face,
• the opening includes an annular space in contact with the first end face,
• an outer diameter of the annular space is larger than an outer diameter of a space located on an opposite side of the first end face in the opening,
• the central conductor includes a first section having a first thickness and a second section having a second thickness smaller than the first thickness and located within the dielectric, at least a part of the first section projecting from the first end face,
• an end of the first section on an anti-projection side is located between the first end face and a specific position within the dielectric in a longitudinal direction of the central conductor, and
• the specific position is a position separated from the first end face toward an inside of the dielectric by ⅛ of an effective wavelength of a transmission signal.